A federated share can report unlimited quota as -3, so the
ajax/upload.php code needs to be adjusted to block uploads when the free
space is unlimited.

When receiving a shared file, the quota for that file counts in the
owner's storage, not the current user's storage.

To make it possible to overwrite the file even when the current user
doesn't have enough space, the quota check is deferred for such files.

The public page now uses the public.php/webdav endpoint.

Also enabled more file operations like rename, move, delete and create
folder from the public page, which are now all possible thanks to the
public.php/webdav endpoint.

".." are valid in folder names, only ".." by itself is invalid
fix for #18987

We need to check if the path exists and throw an error instead of handling this situation ungraciously.

This reverts commit 6a1a4880.

This enforces proper types on POST and GET arguments where I considered it sensible. I didn't update some as I don't know what kind of values they would support 

Fixes https://github.com/owncloud/core/issues/14196 for core

This conversions are actually totally unneeded and probably left-overs from ages where the safe_mode was still a valid thing.

maintain deprecated \OC::$session when getting or setting the session via the server container or UserSession

restore order os OC::$session and OC::$CLI

remove unneded initialization of dummy session

write back session when $useCustomSession is true

log warning when deprecated app is used

Files app:

- removed file list template, now rendering list from JSON response
- FileList.addFile/addDir is now FileList.add() and takes a JS map with all required
  arguments instead of having a long number of function arguments
- added unit tests for many FileList operations
- fixed newfile.php, newfolder.php and rename.php to return the file's
  full JSON on success
- removed obsolete/unused undo code
- removed download_url / loading options, now using
  Files.getDownloadUrl() for that
- server side now uses Helper::getFileInfo() to prepare file JSON response
- previews are now client-side only

Breadcrumbs are now JS only:

- Added BreadCrumb class to handle breadcrumb rendering and events
- Added unit test for BreadCrumb class
- Moved all relevant JS functions to the BreadCrumb class

Public page now uses ajax to load the file list:

- Added Helper class in sharing app to make it easier to authenticate
  and retrieve the file's real path
- Added ajax/list.php to retrieve the file list
- Fixed FileActions and FileList to work with the ajax list

Core:

- Fixed file picker dialog to use the same list format as files app

The encryption app needs to create keys when uploading files, so the
session needs to be kept open in such case.

Fix issue #7152

Fix Issue #6683

Whent trying to upload/rename/create files in a folder that was removed
or rename, the correct error message is now shown.

In the case of upload of multiple files, the upload is cancelled.

This situation can happen if the target folder was renamed or removed
from another browser window or client.

OC_Util::setupFS($user) will create a data dir for the given string - no matter if the user really exists - OCP\JSON::checkUserExists($owner); introduces a ready to use check which will bail out with an JSON error

Fixes #5534

Fixes #5370

Fixes #5328

when _ is left in namespace and files are named after their classes the autoloader will also find classes in the lib folder of an app
its magic!