fix saml users displayname

[ArtificialOwl]

• fix users display name update by using IUser API instead of Accounts
• add occ command to update single display name
• add occ command to update full list of users from the table user_saml_users

[ArtificialOwl]

/backport to stable29

[backportbot[bot]]

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/1584/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 3ba77311

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/1584/stable29

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.