Quota check for shared storage doesn't kick in for received shares in new DAV endpoint

[PVince81]

Steps

1. Create two users "user1" and "user2"
2. Set quota of "user1" to unlimited
3. Set quota of "user2" to 2 MB
4. Login as "user2"
5. Create a folder "shared_by_user2"
6. Share it with "user1"
7. Login as "user1"
8. Start cadaver using the new dav endpoint: "remote.php/dav/files/user1"
9. Upload a 10+ MB file into the root
10. Upload a 10+ MB file into the received folder "shared_by_user2"

Expected result

Upload works into the root.
Upload fails into the received folder due to quota.

Actual result

Upload works in both cases. The quota check doesn't kick in for mounted shared folders.

Versions

Observed in 10.0.2 using the desktop client 2.3.2.
Reported as regression here #14600 (comment)

[PVince81]

a quick debug shows that the wrong path is used when checking quota, basically it tries to fetch the quota from "files/files/user1/shared_with_user2/testfile.dat" which looks like the new DAV prefix...

[PVince81]

which basically means this never worked before, so not technically a server regression... but still, only happening now that the newer clients are using the new DAV endpoint.

PR incoming with further research...

[PVince81]

Raised owncloud/QA#461 to increase automated test coverage

[PVince81]

PR here #28160

[PVince81]

Additional issue: when using chunk upload on new DAV endpoint, it doesn't trigger QuotaPlugin at all because it's a MOVE operation, not PUT...