URLGenerator should also generate OCS urls

[rullzer]

Now that the AppFramework supports OCS alerady for quite some time. We should make sure we can also generate proper urls for it with the url generator.

[nextcloud-bot]

GitMate.io thinks possibly related issues are #4397 (Naughty words in generated URLs), #10471 (Improve URL detection), #3462 (wrong url to doc), #9005 (c), and #6271 (Theming kills pretty URL).