Add support for Cloudflare R2 Buckets

[JonasHiltl]

Motivation and context

It is currently not possible to add a Cloudflare R2 Bucket as a Cloud Storage source, since the Secret access key of R2 has a length of 64 but the ui/serializer restricts the length to 44.

This issue addresses the same problem when using STORJ but with a max length of 128.

For me it would make the most sense to completely remove the max length, but this PR currently only fixes the R2 compatibility by increasing the max length to 64.

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into the CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[codecov]

Codecov Report

Merging #6701 (0990f95) into develop (b450b44) will decrease coverage by 0.04%.
Report is 13 commits behind head on develop.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6701      +/-   ##
===========================================
- Coverage    82.59%   82.55%   -0.04%     
===========================================
  Files          360      360              
  Lines        38926    38977      +51     
  Branches      3570     3577       +7     
===========================================
+ Hits         32150    32179      +29     
- Misses        6776     6798      +22     

Components	Coverage Δ
cvat-ui	77.54% <100.00%> (-0.06%)	⬇️
cvat-server	87.16% <100.00%> (+<0.01%)	⬆️

[Marishka17]

I guess it's OK for now, but we probably need to remove the restriction for a secret key at all, because if I understand correctly AWS has no restriction for a Secret Access Key (only for access key id). And we support other providers (like Oracle OCI and Cloudflare R2) only because they have compatible API with AWS S3, so we have to rely on the AWS S3 limitations.

[nmanovic]

@JonasHiltl , thank you for the great contribution. I'm ready to merge the PR. We have slightly changed how we are updating CHANGELOG. Could you please remove the line from CHANGELOG and use scriv create --edit command (please look at the latest version of CHANGELOG.md file)?

[JonasHiltl]

@nmanovic Thanks for coming back to me, I updated the Changelog entry and I'm looking forward to seeing this get merged.