Support filter on tag id in target endpoint

[bobvandevijver]

I'd like to be able to create a device filter based on tag ID, as the tag ID will be static while the tag name might not be.

As example, I want all devices using the tag with ID 11, which would be tag.id==11 as q:

curl -X 'GET' \
  'https://hawkbit-dev.example.com/rest/v1/targets?q=tag.id%3D%3D11&offset=0&limit=50' \
  -H 'accept: application/hal+json' \
  -H 'Authorization: Basic snip'

The following is returned:

{
  "exceptionClass": "org.eclipse.hawkbit.repository.exception.RSQLParameterUnsupportedFieldException",
  "errorCode": "hawkbit.server.error.rest.param.rsqlInvalidField",
  "message": "The given search field {tag.id} has unsupported sub-attributes. Supported sub-attributes are [name]"
}

I'm aware that there is an endpoint to retrieve all target assigned a specific tag (/rest/v1/targettags/{targetTagId}/assigned), but I need the filter support to be able to create a rollout from it.