registry metadata as API

[mattiaerre]

Description

it would be nice to have registry's metadata info exposed as an API; such as a list of available dependencies as well as plugins; @corlobepy @wmelani and myself will be more than happy to propose a PR that accommodates this need.

// cc @matteofigus @nickbalestra

[matteofigus]

I think it's a good idea.
A couple of considerations about the implementation:

1. You want the api not to conflict with any component name. We use ~ with other endpoints as that's not allowed in a component name. So perhaps it could be something like registry.com/~/api/plugins or registry.com/~api/plugins/ or maybe registry.com/~registry/plugins? (same would apply for dependencies).
2. Dependencies and plugins are private and we possibly don't want to expose them without authentication. I think the simpler thing to do now is to have those endpoints to return JSON in case of discovery:true setting, and a 401 (unauthorised) if discovery:false.
3. When designing the dependencies endpoint, we need to be prepared to the multi-versioned dependencies that we are gonna soon support
4. I have a separate issue Expose plugins via the Registry UI #489 to show the available plugins via UI. One thing I was thinking about is that atm, the registry, apart from the name of the plugin and the actual handler, knows nothing more. I was thinking about making the interface of the plugins extensible to include some docs or links to them, so that exposing the list becomes a bit more useful from a developer's perspective. Perhaps we could open a separate story for that.

[mattiaerre]

closing this issue 👋