Define & Standardize crawler source data workflow

[gzt5142]

The workflow by which crawler sources are defined and included in the ingest/harvest process is loosely defined. The storage mechanism needs formal definition also ( See #281 ).

To-Do:

• Define and document crawler data maintenance workflow
  • How are sources stored and structured? (JSON, CSV, SQL, etc)
  • How are new sources included?
  • How is an existing data source modified?
  • What is the update cycle?
• Create standardized python functions/objects/methods for use across the whole project.
  • pydantic and/or ORM models to define schema and validation rules
  • Validation of sources -- define the requirements for a source to be ingestible.
• Adapt the crawler source to populate its source table from arbitrary store (see Repository Pattern gzt5142/nldi-crawler-py#33); code to interface rather than implementation.