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.