fix(worker): Handle malformed JWT with an HTTP 400 response

[nellh]

Provide HTTP clients (special remotes) feedback when a JWT could not be parsed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 42.41%. Comparing base (9afe434) to head (415b60b).

Files	Patch %	Lines
...ervices/datalad/datalad_service/middleware/auth.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3062      +/-   ##
==========================================
- Coverage   42.42%   42.41%   -0.01%     
==========================================
  Files         601      601              
  Lines       37939    37944       +5     
  Branches     1113     1113              
==========================================
  Hits        16095    16095              
- Misses      21628    21633       +5     
  Partials      216      216              

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