fix: Allow login for limited federation instances

[kescherCode]

Addresses #637

[grishka]

So you're finding an existing session for that instance, and then making a request under that session? That won't address the most popular case when you don't have any sessions on that instance to begin with.

[kescherCode]

Check https://cts.kescher.at/about to see why this isn't possible.

You can't see any info about a limited federation instance while not logged in (which is what I am assuming you mean with "the most popular case"). Since there will be an error anyway, "about the instance" can only ever be viewed while logged in to begin with.

[kescherCode]

(previous force push was merely an indentation fix)

[kescherCode]

See also:

https://github.com/mastodon/mastodon/blob/f92d8c654df654538096efff05e9b1a989d01490/app/controllers/api/v1/instances_controller.rb#L4

https://github.com/mastodon/mastodon/blob/f92d8c654df654538096efff05e9b1a989d01490/app/controllers/api/v1/custom_emojis_controller.rb#L4

[grishka]

Still, how do you get that first session going? How common is it to have multiple accounts on the same server?

[kescherCode]

The first session, you get going by logging in. That's what the first commit in this PR fixes. The second commit are fixes that only apply after logging in.

It doesn't matter how common multiple accounts on the same instance are, does it? I certainly do have that use-case, however.

If you're wondering why I'm just picking any account with a given domain: That's because picking the actual account it would apply to is pretty hard. If you want to, I could force the current account ID to be passed into all methods requiring it.

[grishka]

Sorry, I didn't notice the part where it shows a confirmation alert.

[kescherCode]

Any updates on merging this? The app literally crashes without this PR, so declaring an intent on eventually merging this (or not, you know, that's fine) would be neat.