entity api should return HTTP 204 status code and no body when entity does not exist

[reubenmiller]

Is your feature improvement request related to a problem? Please describe.

Follow the REST API guidelines for deletion of entities from the entity store, so that it is easier for users to consume and reason with.

Describe the solution you'd like

When using the DELETE http://localhost:8000/tedge/entity-store/v1/entities/{topic-id} API, if no entities are deleted because the given topic-id does not exist, then return a response in the following format:

State	HTTP Status	Body
Current	200	[]
Expected	204	empty body

Describe alternatives you've considered

Additional context