make table name configurable for db user backend

[icewind1991]

The main use case for this is to make it easy to create a separate user backend for the guest app (to prevent guests from becoming "real" users if the app gets disabled for any reason).

[codecov]

Codecov Report

Merging #9868 into master will decrease coverage by <.01%.
The diff coverage is 90%.

@@             Coverage Diff              @@
##             master    #9868      +/-   ##
============================================
- Coverage     52.07%   52.07%   -0.01%     
  Complexity    25901    25901              
============================================
  Files          1642     1642              
  Lines         95884    95885       +1     
  Branches       1318     1318              
============================================
  Hits          49929    49929              
- Misses        45955    45956       +1

Impacted Files	Coverage Δ	Complexity Δ
lib/private/User/Database.php	81.36% <90%> (+0.11%)	42 <2> (ø)	⬇️
apps/files_trashbin/lib/Expiration.php	90.32% <0%> (-1.62%)	29% <0%> (ø)

[rullzer]

Would it not be 'safer' to just have the guest app have its own tables? And implement a real backend?

[blizzz]

I guess he wants to save some code, but then this is not in the public namespace either

[rullzer]

I would really prefer to do it properly in its own backend. That way if we want to change something in either the app backend or the db user backend we can do so without worrying of breaking the other.

[icewind1991]

Creating a separate backend would be an almost complete copy paste from this backend

[icewind1991]

I created a separate PR with all changes from this one except the configurable table name

#9881

[MorrisJobke]

I created a separate PR with all changes from this one except the configurable table name

Rebased after #9881 was merged ;)

[MorrisJobke]

I'm fine with this one.

[rullzer]

Ok fair enough. Lets do it like this. if it turns out it diverges to much we can later always move this over to the app.

So 👍 for now :D