Feature/add table support

[scaryclam]

This adds some support for creating sqlalchemy Table object inserts.

This is mainly to aid in the support of M2M relations in projects that use Table rather than Model.

The PR should be considered a WIP for now as I'd like some feedback on whether the approach is acceptable.

[heavenshell]

@scaryclam Thank you for your PR!
I'll look it into later.

BTW, tests are failed. Could you check?
https://travis-ci.org/heavenshell/py-sqlalchemy_seed/jobs/549389130#L557-L558

[heavenshell]

Please add session to docstring param 😉

[heavenshell]

Please add new test case, such as test_load_table_fixtures.
I want test_load_fixtures assure not BCBreak 😌

[heavenshell]

🙆‍♂

[heavenshell]

I'm not familier with Table so, if I say something wrong with this review, please point out 😉
What happen if insert failed. Does DB rollback?

What about do something like followings?
Is this satisfy your requirements? 😄
I want controll session flush, commit, rollback at same place.
IMO it's readable 😉

def _create_table_object_data(fixture, session):
    """Create a Table object entry.

    :param fixture: Fixtures
    :param session: Session
    """
    table_values = []
    for data in fixture:
        if 'table' in data:
            module_name, class_name = data['table'].rsplit('.', 1)
            importlib.import_module(module_name)
            metadata = MetaData()
            metadata.reflect(bind=session.get_bind())
            table = metadata.tables[class_name]
            insert = table.insert()
            insert.values(**data['fields'])
            table_values.append(insert)

    return table_values

def load_fixtures(session, fixtures):
    """Load fixture.

    :param base: `sqlalchemy.ext.declarative`
    :param fixtures: Fixture files
    """
    instances = []
    tables = []
    for fixture in fixtures:
        _instances = _create_model_instance(fixture)
        for instance in _instances:
            instances.append(instance)
        _tables = _create_table_object_data(fixture, session)
        for table in _tables:
            tables.append(table)

    try:
        for instance in instances:
            session.merge(instance)

        for table in tables:
            session.execute(table)
        session.flush()
        session.commit()
    except Exception:
        session.rollback()
        raise

[heavenshell]

nn- I think I wrote something strange? 🤔

[heavenshell]

Thank you for PR.
I added some review comments. Please check it 😄

Yaml defeinition is LGTM.