Fix for issue #4370 - Cpprest does not set Content-Type header on POST requests. (#4374)

* Fixed cpprest generator to include Content-Type header in requests.

* Fixing indent to use spaces.

modules/swagger-codegen/src/main/resources/cpprest/api-source.mustache

@@ -180,7 +180,10 @@ pplx::task<{{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}void{{/r
     else
     {
         throw ApiException(415, U("{{classname}}->{{operationId}} does not consume any supported media type"));
-    }    
+    }
+    
+    //Set the request content type in the header.
+    headerParams[U("Content-Type")] = requestHttpContentType;
     
     {{#authMethods}}
     // authentication ({{name}}) required