Optimise images when they are uploaded and save in webp format

[lkeegan]

• backend
  • open uploaded images using pillow
  • resize if width > 1024
  • export to webp format using pywebp
  • add some png & jpeg files to the tests
• frontend-admin
  • allow png uploads as well as jpg
• frontend
  • update image urls
• resolves Optimize image sizes #166

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 81.81818% with 4 lines in your changes missing coverage. Please review.

Project coverage is 30.09%. Comparing base (e355a44) to head (8e56030).

Files with missing lines	Patch %	Lines
frontend/src/lib/admin.svelte.ts	0.00%	1 Missing ⚠️
...src/lib/components/Admin/EditMilestoneModal.svelte	0.00%	1 Missing ⚠️
...nd/src/lib/components/Admin/MilestoneGroups.svelte	0.00%	1 Missing ⚠️
frontend/src/lib/components/Milestone.svelte	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #177      +/-   ##
==========================================
+ Coverage   30.00%   30.09%   +0.08%     
==========================================
  Files          98       98              
  Lines        3236     3240       +4     
  Branches       86       86              
==========================================
+ Hits          971      975       +4     
  Misses       2194     2194              
  Partials       71       71              

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[MaHaWo]

Nice improvement. Code looks good, but it seems it breaks the childrengallery:

• when I add an image for a child, it cannot be retrieved:

Error in server request
Failed to execute 'createObjectURL' on 'URL': Overload resolution failed.

should we remove the image display for children altogether first? From the discussion about the default image I gathered that this is not desired anymore? Or did that just apply to the default image?

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[lkeegan]

Nice improvement. Code looks good, but it seems it breaks the childrengallery:

• when I add an image for a child, it cannot be retrieved:

Error in server request
Failed to execute 'createObjectURL' on 'URL': Overload resolution failed.

good catch - should be fixed by 8e56030

should we remove the image display for children altogether first? From the discussion about the default image I gathered that this is not desired anymore? Or did that just apply to the default image?

I understood that it only applied to the default image, which was not wanted, but we should still show an image if the user provides one.