fix(db): sqlalchemy 2.0 _entities attr

[wssheldon]

Tests

python -c "from sqlalchemy.orm import Session; from dispatch.database.core import engine; from dispatch.database.service import get_query_models; from dispatch.case.models import Case; from dispatch.tag.models import Tag; session = Session(engine); query = session.query(Case).join(Case.t
ags); models = get_query_models(query); print(f'Models found in joined query: {list(models.keys())}')"
Models found in joined query: ['Case', 'Tag']

python -c "from sqlalchemy.orm import Session; from dispatch.database.core import engine; from dispatch.search.fulltext import search; from dispatch.case.models import Case; from dispatch.tag.models import Tag; session = Session(engine); query = session.query(Case).join(Case.tags); resul
t = search(query, 'test'); print('End-to-end search executed successfully')"
End-to-end search executed successfully

I also tested case name search functionality via the FTS search bar and got the expected results without error.