Add missing type hints to tests.handlers. (#14680)

changelog.d/14680.misc

mypy.ini

synapse/handlers/auth.py

tests/handlers/test_appservice.py

tests/handlers/test_cas.py

tests/handlers/test_directory.py

tests/handlers/test_e2e_room_keys.py

tests/handlers/test_federation.py

tests/handlers/test_federation_event.py

tests/handlers/test_message.py

tests/handlers/test_oidc.py

tests/handlers/test_password_providers.py

tests/handlers/test_presence.py

tests/handlers/test_profile.py

tests/handlers/test_receipts.py

tests/handlers/test_register.py

tests/handlers/test_room.py

tests/handlers/test_room_summary.py

tests/handlers/test_saml.py

tests/handlers/test_send_email.py