Display delegated section in common settings for delegated non-admin

[printminion-co]

Summary

IDeclarativeSettingsForm can't be delegated and can be shown only to admin. Lets not load IDeclarativeSettings for non admins. Otherwise we get "Access forbidden" while displaying /settings/admin and prevent to show delegated sections to non admin like:

Background jobs OCA\Settings\Settings\Admin\Server
Email server OCA\Settings\Settings\Admin\Mail

Before state

# create group1
occ group:add group1

# create user  
OC_PASS=g1user1 ./occ user:add --password-from-env --display-name g1user1 --group group1  -- g1user1


# delegate Mail setting so group1 
./occ admin-delegation:add OCA\\Settings\\Settings\\Admin\\Mail group1

• login and check Administration * Basic Settings
  e.g. open http://localhost:8080/index.php/settings/admin

• Observe: Access forbidden

After state

Todo

• validate delegated configurations can be used by group users with delegation

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[come-nc]

(sorry, I confused tabs, ignore my last changes here)

[provokateurin]

LGTM

[github-actions]

Hello there,
Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the review process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR review process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!

(If you believe you should not receive this message, you can add yourself to the blocklist.)

[come-nc]

Hello, thank you for the PR.
Could you instead use a try/catch around the call to getFormsWithValues ?
If you catch OC\AppFramework\Middleware\Security\Exceptions\NotAdminException you can simply continue with an empty array for declarative settings.

That avoid duplicating the logic for testing admin rights, and if later declarative settings support delegation it will keep working.