For one-2-many and many-2-many relationships, allow the create and
update routes to accept a partial object in the foreign key attribute.
For example:

	client.post("/heros", json={
	    "name": Bob,
	    "team": {"name": "Avengers"}
	}

Assuming there is already a team called Avengers, Bob will be
created, the Team with name "Avengers" will be looked up
and used to populate Bob's team_id foreign key attribute.

The only setup required is for the input model for the
foreign object to specify the Table class that can be used
to lookup the object.

For example:

	class Team(Base):
	    """Team DTO."""

	    __tablename__ = "teams"

	    id = Column(Integer, primary_key=True, index=True)
	    name = Column(String, unique=True)

	class TeamUpdate(Model):
	    name: str

	    class Meta:
	        orm_model = Team