fix: removing surplus slash, making logs richer

[javanlacerda]

Summary

During the validations, we noticed that the the template for source-repository-ref for gitlab has a surplus slash.
We also noticed that the error with log "value <> not present in either claims or defaults. has spawned several times in production, but we wasn't able to detect the reason for it, then I decided to put at least the issuer that triggered the flow on the error log.
I also added a validation that the metadata should exist for ci-providers.

Release Note

Documentation

cc @haydentherapper

[codecov]

Codecov Report

Attention: Patch coverage is 63.63636% with 4 lines in your changes missing coverage. Please review.

Project coverage is 50.26%. Comparing base (cf238ac) to head (040596e).
Report is 172 commits behind head on main.

Files	Patch %	Lines
pkg/identity/ciprovider/principal.go	63.63%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1762      +/-   ##
==========================================
- Coverage   57.93%   50.26%   -7.68%     
==========================================
  Files          50       70      +20     
  Lines        3119     4166    +1047     
==========================================
+ Hits         1807     2094     +287     
- Misses       1154     1841     +687     
- Partials      158      231      +73     

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