"fastapi dev" flow

[1st1]

1. fastapi dev should work out of the box. Ideal setup: a user starts a new fastapi project, imports gel, runs 'gel init', and the rest (1️⃣ watching, 2️⃣ reflecting schema, 3️⃣ backups) is set up automatically.

2. There should be a way to opt-out, via:

   • a setting in pyproject.toml [tools.gel]
     • scenario: you work alone, or the team doesn't want this)
   • via an env var GEL_FASTAPI_DEV=disabled
     • scenario: CI or some other weird edge case
   • in the future we should add support for .env.local themselves by having .no_gel_fastapi_dev file and ignoring it

3. We need gel watch to accept command line arg gel watch --extend-gel-toml FILE with a location of a additional gel.toml file that might have additional hooks/settings. That additional file will not override, but will extend via

   gel.toml:

   [hooks]  # <--- new thing
   schema.update.after="cmd0"
   

   --extend-gel-toml:

   [hooks-extend]  # <--- new thing
   schema.update.after="cmd1"
   

   then the actual hook will be cmd0 && cmd1