DefaultController: catch oauth exceptions during login

[agoujot]

Nothing else to say?

[codecov]

Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.78%. Comparing base (4b8eb28) to head (1bedf66).
⚠️ Report is 226 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Controller/DefaultController.php	0.00%	10 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##               main     #580       +/-   ##
=============================================
- Coverage     71.30%   60.78%   -10.53%     
- Complexity     1275     1407      +132     
=============================================
  Files            46       46               
  Lines          3792     4307      +515     
=============================================
- Hits           2704     2618       -86     
- Misses         1088     1689      +601     

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[agoujot]

D'you mind taking a look? We've been getting quite many failmails about this.