Generalize schema with easier to understand models

[valenzuelaomar]

Think about whether we can have a test schema that's more generic (authors & books maybe?) and take steps to update the test app schema & tests to reflect a less czid-specific schema.

[valenzuelaomar]

It may be good to generate an ER diagram of the schema first to visualize the relationships between the models, then see where the generic models can fit in