added accept and content-type headers to VST messages

Author: rashtao

ChangeLog.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 
 ## [Unreleased]
 
+- fixed VST communication adding `accept` and `content-type` headers
+
 ## [6.7.0] - 2020-07-01
 
 - added support of schema validation (ArangoDB v3.7)

src/main/java/com/arangodb/internal/velocystream/VstCommunication.java

@@ -149,7 +149,9 @@ protected Response createResponse(final Message message) throws VPackParserExcep
         return response;
     }
 
-    protected Message createMessage(final Request request) throws VPackParserException {
+    protected final Message createMessage(final Request request) throws VPackParserException {
+        request.putHeaderParam("accept", "application/x-velocypack");
+        request.putHeaderParam("content-type", "application/x-velocypack");
         final long id = mId.incrementAndGet();
         return new Message(id, util.serialize(request), request.getBody());
     }