This adds a lightweight public interface for handling manual file locking within the files_lock app and to allow other apps like Text, Collabora or ONLYOFFICE to integrate with it.

Required for nextcloud/files_lock#54

Locks are separated into three different types:

• 0 User owned manual lock:
  This lock type is initiated by a user manually through the WebUI or Clients and will limit editing capabilities on the file to the lock owning user.
• 1 App owned lock:
  This lock type is created by collaborative apps like Text or Office to avoid outside changes through WevDAV or other apps.
• 2 Token owned lock: (not implemented yet) This lock type will bind the ownership to the provided lock token. Any request that aims to modify the file will be required to sent the token, the user itself is not able to write to files without the token. This will allow to limit the locking to an individual client.

The OCP parts are mainly for exposing the ability to lock/unlock for apps and to give the files_lock app a way to register and then be triggered by the apps while the actual locking implementation is kept in the LockProvider and DAV Plugin from files_lock app.

Registering through IBootstrap was considered, but decided against as this is only limited to the one app.

App integrations

• Implement collaborative locking text#2248
• Locking richdocuments#2104