Consider adding validation to InternalId

Consider adding a validation to InternalId to require either namespace_id or project_id

Just in case a usage of InternalId creeps in which is out of namespace and project.

The following discussion from !135241 (merged) should be addressed:

• @manojmj started a discussion: (+4 comments)

  Table:

  CREATE TABLE internal_ids (
      id bigint NOT NULL,
      project_id integer,
      usage integer NOT NULL,
      last_value integer NOT NULL,
      namespace_id integer
  );

  and the model has

    belongs_to :project
    belongs_to :namespace

  Since this table is used to supply internal ids to projects or namespaces, and since projects/namespaces are cell-local data, this can be too?

/cc @manojmj @DylanGriffith