Remove onbuild commands and force consumers to explicitly add config (#250)

diff --git a/Dockerfile b/Dockerfile
index 9c70e35..a4bce83 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -179,12 +179,10 @@
     && rm -rf /tmp/api-gateway
 
 COPY init.sh /etc/init-container.sh
-ONBUILD COPY init.sh /etc/init-container.sh
 # add the default configuration for the Gateway
 COPY . /etc/api-gateway
 RUN adduser -S nginx-api-gateway \
     && addgroup -S nginx-api-gateway
-ONBUILD COPY . /etc/api-gateway
 
 EXPOSE 80 8080 8423 9000