[BB-1873] Add v2 of account and instance config APIs
Created by: xitij2000
This PR adds new API endpoints to power the new React-based registration flow. It also adds support Swagger API documentation via drf_yasg
to enable automatic generation of an API Client. It also moves all existing API from before this PR into the v1 namespace.
Under the v2 namespace it adds:
- /v2/accounts/ Accounts API: This API enables public registration, account validation, and allows fetching and updating account data.
- /v2/instances/openedx_config OpenedX instance configuration API: This allows new users to register their first instance and to update their instances' configuration and to provision a new server for it after changes are complete.