[web] Make "Login again" Button configurable

[exalate-issue-sync]

Description

User Stories

• As a user who sees the "Login in again" page I want to get redirected to a valid login page so that I can login.

Value

Acceptance Criteria

• add config option (defaults as is currently)
• if option is set, default gets overwritten

Implementation note: the uri can also be automatically set via the well-known endpoint

Definition of ready

[ ] everybody needs to understand the value written in the user story
[ ] acceptance criteria has to be defined
[ ] all dependencies of the user story need to be identified
[ ] feature should be seen from an end user perspective
[ ] user story has to be estimated
[ ] story points need to be less then 20

Definition of done

• Functional requirements
  [ ] functionality described in the user story works
  [ ] acceptance criteria are fulfilled
• Quality
  [ ] code review happened
  [ ] CI is green
  [ ] critical code received unit tests by the developer
  [ ] automated tests passed (if automated tests are not available, this test needs to be created and passed
• Non-functional requirements
  [ ] no sonar cloud issues