fix(CalDAV): Check for user status before serving public calendars

[DerDreschner]

Summary

This PR adds support for the hide_disabled_user_shares setting on calendars.

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)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[DerDreschner]

/backport to stable34

[DerDreschner]

/backport to stable33

[DerDreschner]

/backport to stable32

[kesselb]

null !== false ;)

Unlikely state I know, but found it still weird while reading the code.

[susnux]

This should at least throw so that we know about this happening instead of silently succeed.
Or handle null just like false and do

Suggested change

	return $this->userManager->get((string)$name)?->isEnabled() !== false;
	return $this->userManager->get((string)$name)?->isEnabled() === true;

[backportbot]

The backport to stable32 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable32
git pull origin stable32

# Create the new backport branch
git checkout -b backport/63004/stable32

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick f1838ab8

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/63004/stable32

Error: Failed to check for changes with origin/stable32: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[backportbot]

The backport to stable33 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable33
git pull origin stable33

# Create the new backport branch
git checkout -b backport/63004/stable33

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick f1838ab8

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/63004/stable33

Error: Failed to check for changes with origin/stable33: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[backportbot]

The backport to stable34 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable34
git pull origin stable34

# Create the new backport branch
git checkout -b backport/63004/stable34

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick f1838ab8

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/63004/stable34

Error: Failed to check for changes with origin/stable34: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[DerDreschner]

Manual backports opened - please review