refactor: Add more logs

[mzaniolo]

While testing I was missing this log to know why the login was failing. Since we usually run the modules with info level I added one more log to help tell what's wrong. I'm not just changing the level of the bellow log because it contains the user external id

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.08%. Comparing base (6014680) to head (3766167).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #72   +/-   ##
=======================================
  Coverage   83.07%   83.08%           
=======================================
  Files          18       18           
  Lines        1873     1874    +1     
  Branches      193      193           
=======================================
+ Hits         1556     1557    +1     
  Misses        234      234           
  Partials       83       83           

Files with missing lines	Coverage Δ
synapse_token_authenticator/token_authenticator.py	71.46% <100.00%> (+0.07%)	⬆️

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