fix(core): support trailingSlash in providerAndAccountId parsing

[ndom91]

☕️ Reasoning

• Support action / providerId paths with trailingSlash enabled (i.e. /api/auth/callback/google/)
• Add three tests, one with default basePath one with custom basePath and one with edge-case multiple trailingSlashes

Fixes #10127

🧢 Checklist

• Documentation
• Tests
• Ready to be merged

🎫 Affected issues

📌 Resources

• Security guidelines
• Contributing guidelines
• Code of conduct
• Contributing to Open Source

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Name	Status	Preview	Comments	Updated (UTC)
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.46%. Comparing base (42ecf79) to head (1e8acb3).

❗ Current head 1e8acb3 differs from pull request most recent head 01408bf. Consider uploading reports for the commit 01408bf to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10752   +/-   ##
=======================================
  Coverage   41.46%   41.46%           
=======================================
  Files         172      172           
  Lines       28236    28236           
  Branches     1171     1171           
=======================================
  Hits        11709    11709           
  Misses      16527    16527           

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