Implement REST API on DRF for the Setting model,
this API will be added to galaxy_ng codebase and exposed though
/settings/ endpoint 

This will replace the current read-only _ui/settings/ and will expose the CRUD for the Django table.

This will include a /settings/schema/ endpoint to provide details for UI when building the settings component.

Add a new key or bump existing key version:
POST /v3/settings/{key} - {"value": str, ...}

Read key value + inspect metadata + schema
GET /v3/settings/{key} - {value, history, schema}

Delete latest version of a key
DELETE /v3/settings/{key} 

Delete all versions of a key
DELETE /v3/settings/{key}/all

Read all version of a key
GET /v3/settings/{key}/all

Read all settings
GET v3/settings/ - {"key": value, ...}

Read all settings schema
GET v3/settings/schema/

Read all settings history
GET v3/settings/inspect/