make `AVAILABLE` the default plugin installPolicy when unset in
`marketplace.json`. similarly, make `ON_INSTALL` the default authPolicy.
this means, when unset, plugins are available to be installed (but not
auto-installed), and the contained connectors will be authed at
install-time.
updated tests.
wire plugin marketplace metadata through app-server endpoints:
- `plugin/list` has `installPolicy` and `authPolicy`
- `plugin/install` has plugin-level `authPolicy`
`plugin/install` also now enforces `NOT_AVAILABLE` `installPolicy` when
installing.
added tests.
#### What
on `plugin/install`, check if installed apps are already authed on
chatgpt, and return list of all apps that are not. clients can use this
list to trigger auth workflows as needed.
checks are best effort based on `codex_apps` loading, much like
`app/list`.
#### Tests
Added integration tests, tested locally.
Support marketplace.json that points to a local file, with
```
"source":
{
"source": "local",
"path": "./plugin-1"
},
```
Add a new plugin/install endpoint which add the plugin to the cache folder and enable it in config.toml.
