* add principal table with dao
* add principal table with dao
* collection saves ownerId instead of owner URL
* save and refresh principals
* show display name of collection owner in GUI
* show only the owner name (preferably) or respective url
* remove principals which do not own any collections
* Don't mock AppDatabase
* ensure we are really dealing with a principal and save it even without its display name
* ensure owner label is hidden when neither owner-displayname nor owner-url are available
* save principal urls without trailing slash
* use a custom query to find principals without collections
* Some changes
- insertOrUpdateByUrl
- don't explicitly set id=0 when not necessary,
- make it work when there are already entries with trailing slahes
- added TODOs
* Small changes
- Update principal only if display name changed
- Rename methods
- Kdoc
- Tests
* stop using simple methods with vague names
* rename method insertOrUpdateOrGet to insertOrUpdate and leave existing kdoc for explanation
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Co-authored-by: Ricki Hirner <hirner@bitfire.at>
