Failure to prepare the storage during backend or auth mechanism
manipulation will throw an InsufficientDataForMeaningfulAnswerException,
which is propagated to StorageNotAvailableException in the filesystem
layer via the FailedStorage helper class.
When a storage is unavailable not due to failure, but due to
insufficient data being available, a special 'indeterminate' status is
returned to the configuration UI.
A backend can now specify generic authentication schemes that it
supports, instead of specifying the parameters for its authentication
method directly. This allows multiple authentication mechanisms to be
implemented for a single scheme, providing altered functionality.
This commit introduces the backend framework for this feature, and so at
this point the UI will be broken as the frontend does not specify the
required information.
Terminology:
- authentication scheme
Parameter interface for the authentication method. A backend
supporting the 'password' scheme accepts two parameters, 'user' and
'password'.
- authentication mechanism
Specific mechanism implementing a scheme. Basic mechanisms may
forward configuration options directly to the backend, more advanced
ones may lookup parameters or retrieve them from the session
New dropdown selector for external storage configurations to select the
authentication mechanism to be used.
Authentication mechanisms can have visibilities, just like backends.
The API was extended too to make it easier to add/remove visibilities.
In addition, the concept of 'allowed visibility' has been introduced, so
a backend/auth mechanism can force a maximum visibility level (e.g.
Local storage type) that cannot be overridden by configuration in the
web UI.
An authentication mechanism is a fully instantiated implementation. This
allows an implementation to have dependencies injected into it, e.g. an
\OCP\IDB for database operations.
When a StorageConfig is being prepared for mounting, the authentication
mechanism implementation has manipulateStorage() called,
which inserts the relevant authentication method options into the
storage ready for mounting.
Backends are registered to the BackendService through new data
structures:
Backends are concrete classes, deriving from
\OCA\Files_External\Lib\Backend\Backend. During construction, the
various configuration parameters of the Backend can be set, in a design
similar to Symfony Console.
DefinitionParameter stores a parameter configuration for an external
storage: name of parameter, human-readable name, type of parameter
(text, password, hidden, checkbox), flags (optional or not).
Storages in the StoragesController now get their parameters validated
server-side (fixes a TODO).
