Changes to POST /consumers/:groupid/instances/:name/offsets

added the optional property validation_errors to the response with the 404 status

the request property offsets/items/offset became required

the request property offsets/items/partition became required

the request property offsets/items/topic became required

removed the success response with the status 200

api tag Consumers added

added optional request body

added the non-success response with the status 404

added the success response with the status 204