Detect mimeType automatically

[Affie]

replace #282

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 3.15%. Comparing base (9b455ee) to head (0e29bf3).
Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/services/BlobStore.jl	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop    #285      +/-   ##
==========================================
- Coverage     3.23%   3.15%   -0.08%     
==========================================
  Files           24      24              
  Lines          803     823      +20     
==========================================
  Hits            26      26              
- Misses         777     797      +20     

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