Add support for OIDC session management error status

[divid3byzero]

Closes/fixes #611

Checklist

• [x] This PR makes changes to the public API
• [x] I have included links for closing relevant issue numbers

[pamapa]

_raiseUserSessionError is never called. What is the difference to _userSessionChanged. Why can't you use that one?

[divid3byzero]

You are right, sorry, I didn't commit everything. I messed up my local development and forgot a few things in the commit after fixing it. I've committed the missing code.

Actually there are use cases when clients want to react to the error status. And as that is something different than the changed status I (and everyone else that wants to react differently to the two statuses) can't use userSessionChanged.

[codecov[bot]]

Codecov Report

Merging #613 (40fb449) into main (809da48) will decrease coverage by 0.20%. The diff coverage is 42.85%.

@@            Coverage Diff             @@
##             main     #613      +/-   ##
==========================================
- Coverage   76.91%   76.71%   -0.21%     
==========================================
  Files          44       44              
  Lines        1590     1602      +12     
  Branches      299      301       +2     
==========================================
+ Hits         1223     1229       +6     
- Misses        336      342       +6     
  Partials       31       31              

Flag	Coverage Δ
unittests	76.71% <42.85%> (-0.21%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/CheckSessionIFrame.ts	3.63% <0.00%> (-0.29%)	:arrow_down:
src/SessionMonitor.ts	14.44% <0.00%> (-0.33%)	:arrow_down:
src/UserManagerEvents.ts	70.27% <100.00%> (+3.60%)	:arrow_up:
src/UserManagerSettings.ts	98.30% <100.00%> (+0.05%)	:arrow_up:

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[phlegx]

Nice work!