feat(storage): add the possibility to customize the rabbitmq content-type

[42atomys]

Relative Issues: Resolve #82

Checklist

• I have linked the relative issue to this pull request
• I have made the modifications or added tests related to my PR
• I have added/updated the documentation for my RP
• I put my PR in Ready for Review only when all the checklist is checked

Breaking changes ?
no

[codecov-commenter]

Codecov Report

Merging #83 (5cdbb3f) into main (5d3acf5) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
+ Coverage   94.22%   94.25%   +0.03%     
==========================================
  Files          22       22              
  Lines         952      957       +5     
==========================================
+ Hits          897      902       +5     
  Misses         37       37              
  Partials       18       18              

Impacted Files	Coverage Δ
pkg/storage/rabbitmq/rabbitmq.go	83.01% <100.00%> (+1.76%)	⬆️

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