Feat: Add private option field for relations

[tanmoyopenroot]

Fixes #6060

Checklist

• Includes tests
• Update documentation

Description of what you did:

This PR adds private option to the relation.

[codecov]

Codecov Report

Merging #8149 into master will increase coverage by 0.24%.
The diff coverage is 47.76%.

@@            Coverage Diff             @@
##           master    #8149      +/-   ##
==========================================
+ Coverage   32.71%   32.95%   +0.24%     
==========================================
  Files        1194     1197       +3     
  Lines       12969    13019      +50     
  Branches     1280     1286       +6     
==========================================
+ Hits         4243     4291      +48     
+ Misses       7886     7885       -1     
- Partials      840      843       +3     

Flag	Coverage Δ
#front	25.05% <16.66%> (+0.25%)	⬆️
#unit	53.88% <50.81%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
...n/src/containers/NotificationProvider/selectors.js	0.00% <0.00%> (ø)
...-manager/admin/src/components/Wysiwyg/constants.js	0.00% <ø> (ø)
...nt-manager/admin/src/components/Wysiwyg/helpers.js	0.00% <ø> (ø)
...lder/admin/src/containers/FormModal/utils/forms.js	22.03% <ø> (+22.03%)	⬆️
...pi-plugin-content-type-builder/utils/attributes.js	30.00% <ø> (ø)
...cumentation/admin/src/containers/HomePage/index.js	0.00% <ø> (ø)
...ugin-upload/admin/src/components/EditForm/index.js	0.00% <0.00%> (ø)
.../containers/InputModalStepper/InputModalStepper.js	0.00% <ø> (ø)
.../src/containers/InputModalStepperProvider/index.js	0.00% <0.00%> (ø)
...-upload/admin/src/containers/ModalStepper/index.js	0.00% <ø> (ø)
... and 27 more

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[HichamELBSI]

Look good to me, thank you for the contribution.

[Convly]

LGTM