Enabling flatenning on empty namespace

[NicoForce]

Comprehensive Summary of your change

• Removes the if condition that skips flatenning when namespace length is 0.
• Adds case in switch for dstRepoPrefix value when namespace length is 0.
• Removed empty namespace test.
• Added 6 new tests for empty namespace behavior.

Issue being fixed

Fixes #19319

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[NicoForce]

@wy65701436 @chlins Is there anything missing that I can do to move this forward? Please let me know, thanks!

[Vad1mo]

Can you elaborate and confirm that your PR is backward compatible and won't break existing setups when applied?
Also the impact on the docs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.79%. Comparing base (a3e1b1e) to head (0a6432f).
Report is 22 commits behind head on main.

❗ Current head 0a6432f differs from pull request most recent head 8a56174. Consider uploading reports for the commit 8a56174 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #19321       +/-   ##
===========================================
- Coverage   67.45%   44.79%   -22.66%     
===========================================
  Files         996      244      -752     
  Lines      109773    13416    -96357     
  Branches     2720     2752       +32     
===========================================
- Hits        74044     6010    -68034     
+ Misses      31747     7100    -24647     
+ Partials     3982      306     -3676     

Flag	Coverage Δ
unittests	44.79% <ø> (-22.66%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 779 files with indirect coverage changes

[NicoForce]

Can you elaborate and confirm that your PR is backward compatible and won't break existing setups when applied? Also the impact on the docs.

It will break existing setups, for those using the empty namespace option, they would need to change to adding the value they were already using to the project name, which is the current default behavior.

The section that needs to be improved in the docs is this one, will create a PR for it.

[github-actions]

This PR is being marked stale due to a period of inactivty. If this PR is still relevant, please comment or remove the stale label. Otherwise, this PR will close in 30 days.

[NicoForce]

Commenting to remove staleness

[github-actions]

This PR is being marked stale due to a period of inactivty. If this PR is still relevant, please comment or remove the stale label. Otherwise, this PR will close in 30 days.

[NicoForce]

Commenting to remove stale label

[mkhpalm]

I would like to see this merged since the existing behavior feels/acts more like a bug than a feature.