Allow Forcing all users to always use SSO

[hardillb]

fixes #6319

Description

Allows configuration of a single SSO provider that all users will be redirected to

Users trying to access /admin/* routes are not redirected to the SSO provider allowing admins to be able to login even when SSO is not working.

Related Issue(s)

#6319

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

❌ Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.27%. Comparing base (2b3a0ec) to head (6121eb8).

Files with missing lines	Patch %	Lines
forge/routes/api/settings.js	16.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7119      +/-   ##
==========================================
- Coverage   76.29%   76.27%   -0.02%     
==========================================
  Files         405      405              
  Lines       20348    20354       +6     
  Branches     4895     4896       +1     
==========================================
+ Hits        15525    15526       +1     
- Misses       4823     4828       +5     

Flag	Coverage Δ
backend	76.27% <16.66%> (-0.02%)	⬇️

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[hardillb]

Possible keycloak option for the logout url

https://suedbroecker.net/2021/05/18/simply-logout-from-keycloak/