Run API Client requests through middleware

[askvortsov1]

Fixes #2474

Changes proposed in this pull request:

• Add integration tests for login and registration; realized that this change might break them and they are currently very missing.
• API client now has a fluent API, and sends via request methods using a path.

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).

[askvortsov1]

Moved the pipe construction into the service provider, this feels a lot cleaner to me.

[askvortsov1]

@clarkwinkelmann I'm a bit conflicted on how to proceed here with regards to #2800.

Just adding the "Start Session" middleware won't fix it, because the session that would get started is different from the one from the original request.

We could add session as an argument, but that would require a lot of code changes, and as you mentioned, wouldn't scale well to other changes.

One idea I had was allowing the entire "parent" request to be passed in as an optional argument after $actor, and then ApiClient could transfer over certain attributes (like session). Actor could still be provided, but if it wasn't, maybe we could read that from the parent request too?

[askvortsov1]

Tests are failing due to the default route setting in DefaultRouteTest

[clarkwinkelmann]

I haven't tested the changes, but here are a few comments based on the code.

I'm not particularly a fan of private statements as I have said before. I'm sure this change will break multiple of my extensions where I will have to copy the whole file instead of just re-implementing getApiDocument (when it's private, not only it cannot be called, but re-implementing it doesn't work without also re-implementing the method that calls it)

Couldn't a method chain maybe make for a cleaner client API? Like $client->withParentRequest($request)->withParams($params)->get('discussions.show') to avoid all the null parameters?

[askvortsov1]

I'm not particularly a fan of private statements as I have said before. I'm sure this change will break multiple of my extensions where I will have to copy the whole file instead of just re-implementing getApiDocument (when it's private, not only it cannot be called, but re-implementing it doesn't work without also re-implementing the method that calls it)

Reverted, not sure why I changed that. Although tbh, the entire Content system needs an extensibility review.

Couldn't a method chain maybe make for a cleaner client API? Like $client->withParentRequest($request)->withParams($params)->get('discussions.show') to avoid all the null parameters?

Agreed, changed. Much nicer, and clearer to read.

[clarkwinkelmann]

Still not tested locally, but it looks really good like this now!

Just one suggestion below.

[clarkwinkelmann]

Looks good.

Just one more thing below.

[SychO9]

I love how much cleaner it is now!