Feature Request: Action Relationship from table to action

Action relationship can be created from an action to a local table.
Please also add support for creating a relationship from a local table to an action.

For instance,
An action accepts `user_id` as the input and return the `first_name`.
A local table includes a list of `user_id`.
And I'd like hasura to return a list of users that contain both `user_id` and `first_name`.