Fix missing task failure error message on Overlord caused by MessageBodyWriter not found error on Middle Manager

[gargvishesh]

Fixes missing task failure error message on Overlord.

The error message was missing since TaskManagementResource#assignTask API wasn't annotated with @Produces(MediaType.APPLICATION_JSON) resulting in the response being treated as application/octet-stream, that in turn lead to MessageBodyWriter not found error on the middle manager. The exception is not logged on the middle manager itself since it happens even before entering the assignTask function -- while mapping arg Task -> MSQControllerTask.

Resolution is to add @Produces annotation to TaskManagementResource#assignTask

Updated error message on Overlord:

org.apache.druid.java.util.common.RE: Failed to assign task[query-50594440-9720-451b-b5c1-76a3d3ff6ffe] to worker[localhost:8091]. Response Code[400] and Message[{"error":"Please make sure to load all the necessary extensions and jars with type 'query_controller'. Could not resolve type id 'query_controller' as a subtype of org.apache.druid.indexing.common.task.Task known type ids = [archive, compact, index, index_hadoop, index_kafka, index_parallel, index_realtime, index_realtime_appenderator, index_sub, kill, move, noop, partial_dimension_cardinality, partial_dimension_distribution, partial_index_generate, partial_index_generic_merge, partial_range_index_generate, restore, single_phase_sub_task]\n at [Source: (org.eclipse.jetty.server.HttpInputOverHTTP); line: -1, column: 10]"}]. Retrying...