Adding placeholders to replace common dependency versions
diff --git a/pom.xml b/pom.xml
index 8815bce..8b2b8be 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="ISO-8859-1"?>
-    <!--
+<!--
         Licensed to the Apache Software Foundation (ASF) under one or more contributor license
         agreements. See the NOTICE file distributed with this work for additional information
         regarding copyright ownership. The ASF licenses this file to you under the Apache License,
@@ -32,12 +32,16 @@
         <connection>scm:git:https://gitbox.apache.org/repos/asf/sling-org-apache-sling-starter.git</connection>
         <developerConnection>scm:git:https://gitbox.apache.org/repos/asf/sling-org-apache-sling-starter.git</developerConnection>
         <url>https://gitbox.apache.org/repos/asf?p=sling-org-apache-sling-starter.git</url>
-      <tag>HEAD</tag>
-  </scm>
+        <tag>HEAD</tag>
+    </scm>
 
     <properties>
         <sling.java.version>8</sling.java.version>
         <IT.expected.bundles.count>126</IT.expected.bundles.count>
+        <jackrabbit.version>2.20.0</jackrabbit.version>
+        <jackson.version>2.11.1</jackson.version>
+        <oak.version>1.26.0</oak.version>
+        <slf4j.version>1.7.25</slf4j.version>
     </properties>
 
     <build>
@@ -108,7 +112,7 @@
                             <classifier>oak_mongo_far</classifier>
                             <includeClassifier>oak_mongo</includeClassifier>
                         </archive>
-                    </archives>                 
+                    </archives>
                 </configuration>
                 <executions>
                     <execution>
@@ -120,8 +124,11 @@
                             <goal>attach-features</goal>
                             <goal>attach-featurearchives</goal>
                         </goals>
+                        <configuration>
+                            <replacePropertyVariables>jackrabbit.version,jackson.version,oak.version,slf4j.version</replacePropertyVariables>
+                        </configuration>
                     </execution>
-               </executions>
+                </executions>
             </plugin>
         </plugins>
 
@@ -142,7 +149,7 @@
             </plugins>
         </pluginManagement>
     </build>
-    
+
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
@@ -163,4 +170,3 @@
         </dependency>
     </dependencies>
 </project>
-
diff --git a/src/main/features/composum_composum-nodes.json b/src/main/features/composum_composum-nodes.json
index 7d69770..408ceb3 100644
--- a/src/main/features/composum_composum-nodes.json
+++ b/src/main/features/composum_composum-nodes.json
@@ -2,27 +2,27 @@
 {
     "id":"org.apache.sling:org.apache.sling.starter:slingfeature:composum_composum-nodes:12-SNAPSHOT",
     "variables":{
-        "composum.nodes.version":"1.11.5"
+        "composum.nodes.version":"1.12.0"
     },
     "bundles":[
         {
-            "id":"com.composum.sling.core:composum-sling-core-commons:1.11.5",
+            "id":"com.composum.sling.core:composum-sling-core-commons:1.12.0",
             "start-order":"20"
         },
         {
-            "id":"com.composum.sling.core:composum-sling-core-console:1.11.5",
+            "id":"com.composum.sling.core:composum-sling-core-console:1.12.0",
             "start-order":"20"
         },
         {
-            "id":"com.composum.sling.core:composum-sling-core-jslibs:1.11.5",
+            "id":"com.composum.sling.core:composum-sling-core-jslibs:1.12.0",
             "start-order":"20"
         },
         {
-            "id":"com.composum.sling.core:composum-sling-package-manager:1.11.5",
+            "id":"com.composum.sling.core:composum-sling-package-manager:1.12.0",
             "start-order":"20"
         },
         {
-            "id":"com.composum.sling.core:composum-sling-user-management:1.11.5",
+            "id":"com.composum.sling.core:composum-sling-user-management:1.12.0",
             "start-order":"20"
         }
     ],
@@ -36,4 +36,4 @@
             "whitelist.name":"composum"
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/features/oak_oak.json b/src/main/features/oak_oak.json
index 694bf7b..dd891e4 100644
--- a/src/main/features/oak_oak.json
+++ b/src/main/features/oak_oak.json
@@ -1,68 +1,65 @@
 
 {
     "id":"org.apache.sling:org.apache.sling.starter:slingfeature:oak:12-SNAPSHOT",
-    "variables":{
-        "oak.version":"1.26.0"
-    },
     "bundles":[
         {
             "id":"org.apache.felix:org.apache.felix.jaas:1.0.2",
             "start-order":"10"
         },
         {
-            "id":"org.apache.jackrabbit:oak-api:1.26.0",
+            "id":"org.apache.jackrabbit:oak-api:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-blob-plugins:1.26.0",
+            "id":"org.apache.jackrabbit:oak-blob-plugins:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-blob:1.26.0",
+            "id":"org.apache.jackrabbit:oak-blob:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-commons:1.26.0",
+            "id":"org.apache.jackrabbit:oak-commons:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-core-spi:1.26.0",
+            "id":"org.apache.jackrabbit:oak-core-spi:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-core:1.26.0",
+            "id":"org.apache.jackrabbit:oak-core:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-jackrabbit-api:1.26.0",
+            "id":"org.apache.jackrabbit:oak-jackrabbit-api:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-jcr:1.26.0",
+            "id":"org.apache.jackrabbit:oak-jcr:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-lucene:1.26.0",
+            "id":"org.apache.jackrabbit:oak-lucene:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-query-spi:1.26.0",
+            "id":"org.apache.jackrabbit:oak-query-spi:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-security-spi:1.26.0",
+            "id":"org.apache.jackrabbit:oak-security-spi:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-store-composite:1.26.0",
+            "id":"org.apache.jackrabbit:oak-store-composite:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-store-document:1.26.0",
+            "id":"org.apache.jackrabbit:oak-store-document:${oak.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:oak-store-spi:1.26.0",
+            "id":"org.apache.jackrabbit:oak-store-spi:${oak.version}",
             "start-order":"15"
         },
         {
diff --git a/src/main/features/sling-models-jacksonexporter_models-jacksonexporter.json b/src/main/features/sling-models-jacksonexporter_models-jacksonexporter.json
index 77f390a..547488c 100644
--- a/src/main/features/sling-models-jacksonexporter_models-jacksonexporter.json
+++ b/src/main/features/sling-models-jacksonexporter_models-jacksonexporter.json
@@ -1,20 +1,17 @@
 
 {
     "id":"org.apache.sling:org.apache.sling.starter:slingfeature:sling-models-jacksonexporter_models-jacksonexporter:12-SNAPSHOT",
-    "variables":{
-        "jackson.version":"2.11.1"
-    },
     "bundles":[
         {
-            "id":"com.fasterxml.jackson.core:jackson-annotations:2.11.1",
+            "id":"com.fasterxml.jackson.core:jackson-annotations:${jackson.version}",
             "start-order":"20"
         },
         {
-            "id":"com.fasterxml.jackson.core:jackson-core:2.11.1",
+            "id":"com.fasterxml.jackson.core:jackson-core:${jackson.version}",
             "start-order":"20"
         },
         {
-            "id":"com.fasterxml.jackson.core:jackson-databind:2.11.1",
+            "id":"com.fasterxml.jackson.core:jackson-databind:${jackson.version}",
             "start-order":"20"
         },
         {
diff --git a/src/main/features/sling_sling.json b/src/main/features/sling_sling.json
index 1ddf965..416c31a 100644
--- a/src/main/features/sling_sling.json
+++ b/src/main/features/sling_sling.json
@@ -1,9 +1,6 @@
 
 {
     "id":"org.apache.sling:org.apache.sling.starter:slingfeature:sling:12-SNAPSHOT",
-    "variables":{
-        "jackrabbit.version":"2.20.0"
-    },
     "bundles":[
         {
             "id":"commons-codec:commons-codec:1.14",
@@ -278,27 +275,27 @@
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-data:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-data:${jackrabbit.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-jcr-commons:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-jcr-commons:${jackrabbit.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-jcr-rmi:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-jcr-rmi:${jackrabbit.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-spi-commons:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-spi-commons:${jackrabbit.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-spi:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-spi:${jackrabbit.version}",
             "start-order":"15"
         },
         {
-            "id":"org.apache.jackrabbit:jackrabbit-webdav:2.20.0",
+            "id":"org.apache.jackrabbit:jackrabbit-webdav:${jackrabbit.version}",
             "start-order":"15"
         },
         {