Add initial tests on the authentication service.

[pixlwave]

Most of the authentication service was untested (and some of the tests were temporarily using live servers). This PR adds a MockAuthenticationRestClient and tests for login/registration. There is room for more tests (and adding an email/MSISDN identifier still needs implementation), but these tests cover the majority of the flow/state and can be added to over time.

Part of #6179 depends on matrix-org/matrix-ios-sdk#1484

[github-actions]

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[aringenbach]

LGTM 👍

Not sure what's up with the GH Action though as I fail loading logs, tests did run successfully for me.

[pixlwave]

Thanks, yeah I'm confused too. Didn't get time to look into it today so will have to have a look next week when I'm back.

[stefanceriu]

The tests look good to me but a lot of them crash (EXC_BAD_ACCESS) now inside the MXRestClient (they work on develop). I believe the same thing happens on the CI but isn't handled properly.
I imagine it's linked to the sessionCreator but I haven't really looked into it.

[pixlwave]

I imagine it's linked to the sessionCreator but I haven't really looked into it.

Bingo! I've added an empty handler in the init as this seems to be expected when the credentials are set (and not checked for nullability) in MXRestClient's init.

[stefanceriu]

👍 👍