fix: Only keep allowed characters in appid, and flag the method as escaping

[come-nc]

• Resolves: #

Summary

There are a few more psalm-taint types than what was listed, and I had to add the phpdoc on the implementation as well to get psalm to take it into account.

I also fixed the FIXME in there by only keeping explicitely allowed characters in appid.
Should be fine as the xsd schema is already enforcing this.

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)

[come-nc]

/backport to stable31

[come-nc]

/backport to stable30

[come-nc]

/backport to stable29

[backportbot]

The backport to stable29 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable29
git pull origin stable29
# Create the new backport branch
git checkout -b backport/50794/stable29
# Cherry pick the change from the commit sha1 of the change against the default branch# This might cause conflicts, resolve them
git cherry-pick 8f57a507 6e7c97ea
# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/50794/stable29

Error: 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 stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30
# Create the new backport branch
git checkout -b backport/50794/stable30
# Cherry pick the change from the commit sha1 of the change against the default branch# This might cause conflicts, resolve them
git cherry-pick 8f57a507 6e7c97ea
# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/50794/stable30

Error: No changes found in backport branch

---

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

[come-nc]

Not backportable to 30, cleanAppId is still in legacy/OC_App on this version.