Raise an exception in create_test_db() if test data contains a key that is not a valid column

[vingkan]

This would save a lot of headaches when creating test data for SQL queries.

[wpj0110]

create_test_db() is in transithealth/api/utils/testing.py for the curious

[wpj0110]

Sample usage of create_test_db() in your jupyter notebooks for your "My Example Notebook"