Add getValue to MessageSpec (#120)

diff --git a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/api/MessageSpec.java b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/api/MessageSpec.java
index d8ac241..394aa36 100644
--- a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/api/MessageSpec.java
+++ b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/api/MessageSpec.java
@@ -57,4 +57,10 @@
 		return null;
 	}
 
+	/**
+	 * Gets the value of this message spec.
+	 * @return the value of this message spec
+	 */
+	T getValue();
+
 }
diff --git a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/DefaultMessageSpec.java b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/DefaultMessageSpec.java
index 8b89945..9635c26 100644
--- a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/DefaultMessageSpec.java
+++ b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/DefaultMessageSpec.java
@@ -121,6 +121,11 @@
 	}
 
 	@Override
+	public T getValue() {
+		return this.value;
+	}
+
+	@Override
 	public String toString() {
 		StringBuilder stringBuilder = new StringBuilder().append("DefaultMessageSpec{");
 		stringBuilder.append("value=").append(this.value);
diff --git a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/ValueOnlyMessageSpec.java b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/ValueOnlyMessageSpec.java
index c29404b..b116477 100644
--- a/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/ValueOnlyMessageSpec.java
+++ b/pulsar-client-reactive-api/src/main/java/org/apache/pulsar/reactive/client/internal/api/ValueOnlyMessageSpec.java
@@ -44,4 +44,9 @@
 		return "ValueOnlyMessageSpec{" + "value=" + this.value + '}';
 	}
 
+	@Override
+	public T getValue() {
+		return this.value;
+	}
+
 }