[FIXIES #13030] Endpoint to delete a resource's thumbnail

[Gpetrak]

This PR is created according to this issue #13030 . The endpoint will delete the thumbnail image from disk and the corresponding database fields: thumbnail_field and thumbnail_path

Checklist

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[giohappy]

@Gpetrak before changing the failing tests please ensure that it's not a temporary failure. Those tests worked fine until now.
In case speak with @mattiagiupponi, which is also the reviewer for your PR.

[codecov]

Codecov Report

Attention: Patch coverage is 92.59259% with 4 lines in your changes missing coverage. Please review.

Project coverage is 68.00%. Comparing base (050aa97) to head (90b6cf2).
Report is 16 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #13032      +/-   ##
==========================================
+ Coverage   67.98%   68.00%   +0.02%     
==========================================
  Files         980      980              
  Lines       59299    59352      +53     
  Branches     6931     6934       +3     
==========================================
+ Hits        40312    40363      +51     
  Misses      17339    17339              
- Partials     1648     1650       +2     

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[Gpetrak]

@Gpetrak before changing the failing tests please ensure that it's not a temporary failure. Those tests worked fine until now.
In case speak with @mattiagiupponi, which is also the reviewer for your PR.

@giohappy finally the test_dataset_permissions test was broken and with the help of @mattiagiupponi the test was fixed and merged to master. Now the tests pass.

[giohappy]

@Gpetrak please add a test for the new endpoint

[Gpetrak]

@giohappy I just added the tests for the delete_thumbnail endpoint

[mattiagiupponi]

Hi @Gpetrak i guess it could be worth to add a test where a user, tries to delete the thumbnail of a resource which does not belong to it.
like user bobby tries to delete the thumbnail of a resource owner by user norm. I suppose the user should not have the right to do it