Add blocking sign in for users not allowed to use password auth for web

What does this MR do?

I noticed that users that are not supposed to be able to log in through password authentication (have allow_password_authentication_for_web? method return false) can log in - in SessionsController it was not checked.

This MR checks during login if user was trying to use username/password couple and if they are allowed to log in like that. If not, they are not being logged in.

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Does this MR meet the acceptance criteria?

Conformity

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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
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Resolves #330497 (closed)