Rearrange backend endpoints for study areas

[dcdenu4]

Keep track of the "study areas" that a user has created, letting them select them in order to create new scenarios, for example.

A Study Area could have many Scenarios, but a Scenario has one Study Area.

Overview of what the backend tables might look like (roughly):

Study Area

• ID
• name
• list of Scenarios (backend convenience)
• list of parcel IDs

Parcel

• WKT (also used to check duplicates)
• ID
• reference to each parcel (address, unique ID) (sent from the frontend if at all)

Scenarios

• ID
• name
• description
• study area ID
• results of wallpapering / painting - maybe just LULC path
• scenario operation ("wallpapering" | "paint")

This will change how some frontend / endpoint api calls are currently managed.

• requesting parcel stats

[dcdenu4]

This is being set up in the frontend-backed-integration branch.

[dcdenu4]

I think we've accomplished this.