[WIP] Change the saml acs endpoint to support _plugin

[RyanL1997]

Description

[Describe what this change achieves]

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)
• Why these changes are required?
• What is the old behavior before changes and new behavior after changes?

Issues Resolved

[List any issues this PR will resolve]

Is this a backport? If so, please add backport PR # and/or commits #

Testing

[Please provide details of testing done: unit testing, integration testing and manual testing]

Check List

• New functionality includes testing
• New functionality has been documented
• Commits are signed per the DCO using --signoff

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For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Merging #3246 (74bb89e) into main (d7eabcf) will decrease coverage by 0.03%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##               main    #3246      +/-   ##
============================================
- Coverage     62.51%   62.49%   -0.03%     
+ Complexity     3403     3400       -3     
============================================
  Files           259      259              
  Lines         20055    20055              
  Branches       3370     3370              
============================================
- Hits          12538    12533       -5     
- Misses         5866     5872       +6     
+ Partials       1651     1650       -1     

Files Changed	Coverage Δ
...zon/dlic/auth/http/saml/Saml2SettingsProvider.java	60.18% <50.00%> (ø)

... and 2 files with indirect coverage changes

[RyanL1997]

Closing this according to #3271