ING-1104: Add support for mutation tokens with MutateIn.

Author: brett19

dataapiv1/spec.yaml

@@ -858,6 +858,8 @@ paths:
           headers:
             ETag:
               $ref: '#/components/headers/ETag'
+            X-CB-MutationToken:
+              $ref: '#/components/headers/MutationToken'
           content:
             application/json:
               schema:

gateway/dapiimpl/server_v1/dataapi_subdoc.go

@@ -306,7 +306,8 @@ func (s *DataApiServer) MutateInDocument(
 
 	resp := dataapiv1.MutateInDocument200JSONResponse{
 		Headers: dataapiv1.MutateInDocument200ResponseHeaders{
-			ETag: casToHttpEtag(result.Cas),
+			ETag:             casToHttpEtag(result.Cas),
+			XCBMutationToken: tokenFromGocbcorex(in.BucketName, result.MutationToken),
 		},
 	}