Need to document how to use pytest

[kelle]

There's pytest for astrodb_utils, but there's pytest for the database, and those are two different things.

Also, need to document workflow for modifying the schema and modifying the tests in conjunction.

[kelle]

if you change the schema, also change the

• test_contents.py

If tables are deleted, template JSON files will have tabular data for non-existent tables. Need to figure out workflow for modifying schema and rewriting JSON files. warn about losing data.