[Task]: Create tables for opportunity attachments

[chouinar]

Summary

We want to create the following tables for storing opportunity attachment information:

Several of these tables have foreign keys to the opportunity table which already exists.

Please create these table models (except the two prefixed by lk_) in the https://github.com/navapbc/simpler-grants-gov/blob/main/api/src/db/models/opportunity_models.py file.

Not included on all of these tables is the updated_at and created_at timestamps, which can be added automatically to the model by adding TimestampMixin as a parent class (ie. your class definition should look like class MyTable(ApiSchemaTable, TimestampMixin):)

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The two lookup tables (prefixed with lk) should be created like our other lookup tables: https://github.com/navapbc/simpler-grants-gov/blob/main/api/src/db/models/lookup_models.py - to do this you'll need to create a Python enum for each and configure it to map to integer values in the DB.

See: https://github.com/navapbc/simpler-grants-gov/blob/main/documentation/api/lookup-values.md for further details on how this works.

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For these two enums, we'll want the following values.

For the opportunity attachment type enum, there are exactly two values:

• related_link -> 1
• attachment -> 2

For the opportunity attachment folder type enum, there are exactly three values:

• full_announcement -> 1
• revised_full_announcement -> 2
• other_supporting_documents -> 3

Acceptance criteria

• Tables created in our SQLAlchemy models
• Migrations created via Alembic
• Lookup table values configured

[acouch]

Issue migrated to HHS#2123