Prevent use of invalid characters for file provider domain names

[claucambra]

Closes #6661

[claucambra]

/backport to stable-3.13

[github-actions]

⚠️ Clang-Tidy found issue(s) with the introduced code (1/1)

[backportbot]

The backport to stable-3.13 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable-3.13
git pull origin stable-3.13

# Create the new backport branch
git checkout -b backport/6669/stable-3.13

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 10faa006

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/6669/stable-3.13

Error: Failed to cherry pick commits: error: no cherry-pick or revert in progress
fatal: cherry-pick failed

---

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

[nextcloud-desktop-bot]

AppImage file: nextcloud-PR-6669-10faa006e7399c9bfeb80a441c85a7962d7e8af6-x86_64.AppImage

To test this change/fix you can simply download above AppImage file and test it.

Please make sure to quit your existing Nextcloud app and backup your data.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud