Support for scripting interface

[veggiesaurus]

The scripting interface is getting migrated from gRPC to simple HTTP (CARTAvis/carta-backend#952). Once @confluence has finished this, we can start adding support for scripting to the controller. The following capabilities are required:

• Allow users to enable or disable scripting. This will determine whether the --enable_scripting flag is passed to their carta_backend process on startup.
• Allow users to generate and revoke API tokens. I think this should behave in a similar manner to the GitHub token page. Users can give tokens a name and choose a token lifetime (30 mins, 3 h, 1 day, etc). Users can also revoke existing tokens and see when they were last used.
• Handle incoming HTTP requests to /api/scripting/* and only proxy those requests with a valid token. This will be done in Proof-of-concept scripting support #109