Express configuration constraints in environment definition

[itowlson]

In addition to limits on which APIs are available, some environments constrain how APIs can be configured. For example, an environment may support only a single "default" key-value store.

While environments can catch this stuff with maximum fidelity at deployment time, it would be nice to find out about it at dev time, before you built too much code that relied on separating your KV stores.

We'd need feedback from env owners on what to constrain but here's my sighting shot on what items could usefully support configuration constraints:

Configuration item	Constrainable
Allowed outbound hosts	No (they can exclude APIs like HTTP, Redis, Postgres, etc. but that's at the interface level; I can't see constraining AOH patterns)
Files	No (they can exclude the filesystem API but not individual patterns, that just seems implausible)
Environment variables	No (they can exclude the env var API but individual variables why)
KV stores	Yes
SQLite databases	Yes
AI models	Yes
Variables	No (can exclude the API but again I can't see why an env could ban individual vars)

[fibonacci1729]

Thanks for capturing this! This is a good starting point that I think we should roll out soon.