Fix setup through nextcloud app (intent) not working

[sunkup]

Purpose

The nextcloud login/setup flow could not be started via intent. This fixes it.

Short description

LoginActivity:

• Now using previously unused intentToInitialLoginType() to determine login type from intent.
• Use selectLoginType() to change the login type accordingly

LoginScreenModel:

• Alter selectLoginType() to also update the ui state of the login details page. Previously it only updated the ui state of the login type page.
• Small lint fix

See also: Creation of intent in nextcloud app.

Testing

Intent for testing:

adb shell am start -e url "https://davtest.dev001.net/nextcloud" -e loginFlow 1  at.bitfire.davdroid/at.bitfire.davdroid.ui.setup.LoginActivity

Checklist

• [X] The PR has a proper title, description and label.
• [x] I have self-reviewed the PR.
• [x] I have added documentation to complex functions and functions that can be used by other modules.
• [X] I have added reasonable tests or consciously decided to not add tests.

[sunkup]

We could use the initial data approach here too:

* pass `initialLoginType` & `initialloginInfo` to the `LoginScreen`

* `LoginScreen` injects/creates the model with the initial data in the constructor

Then we could get rid of the if (savedInstanceState == null) and have better separation of concerns (no direct model access from outside).

While it would have been possible (and shorter in code) I have added an extra startPage parameter as well. The alternative is to infer the starting page from the login type inside the model, which is shorter, but less flexible. I can change that back if you prefer :)

The advantage would be that future intents could start the correct login page more easily.