Report Correct Mime Type

The HttpAppender of Log4j2 will use the content type reported by the layout as
HTTP header. To work well with e.g. Fluent Bit, the reported value was adapted
to the actually generated JSON format.

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>

Author: KarstenSchnitter

cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/layout/JsonPatternLayout.java

@@ -228,4 +228,9 @@ private <P extends ComposerBase> void addStacktrace(ObjectComposer<P> oc, LogEve
         }
     }
 
+    @Override
+    public String getContentType() {
+        return "application/json";
+    }
+
 }