in order to create a 1:1 copy of a file if a version gets created
we need to store this information on copyBetweenStorage(). This
allows us to by-pass the encryption wrapper if we read the source file.
The code path called when using external storage with WebDAV is using `\OC\Files\Storage\Wrapper\Encryption::getMetaData` which did not contain the actual encrypted version inside the cache entry version. This lead to the following:
1. User uploaded a file
2. File is created and `\OC\Files\Storage\Wrapper\Encryption::getMetaData` is called. It has an empty `encryptedVersion` but sets `encrypted` to either `true` or `false`.
3. The call when updating the file cache will use the old version.
In case of a move operation from an unencrypted to an encrypted
storage the old encrypted version would stay with "0" while the
correct value would be "1". Thus we manually set the value to "1"
for those cases.
See also https://github.com/owncloud/core/issues/23078
When calling `\OC\Files\View::copy` we should also keep the version to ensure that the file will always have the correct version attached and can be successfully decrypted.
To test this the following steps are necessary (from https://github.com/owncloud/core/issues/22781#issuecomment-191328982):
1. setup a new ownCloud 9.0 beta2
2. enable encryption
2. upload a docx (5.7MB large)
3. upload the same file again and overwrite the existing file
4. I can download the original file and the first version
5. I restore the first version
6. restored version can no longer be downloaded with the error described above
The manual cache operation in `\OCA\Files_Versions\Storage` is unfortunately necessary since `\OCA\Files_Versions\Storage::copyFileContents` is not using `\OCP\Files\Storage::moveFromStorage` in the case when an object storage is used. Due to the workaround added in 54cea05271 the stream is directly copied and thus bypassing the FS.
Storage status is saved in the database. Failed storages are rechecked every
10 minutes, while working storages are rechecked every request.
Using the files_external app will recheck all external storages when the
settings page is viewed, or whenever an external storage is saved.
Explicitly clear the stat cache after deleting an empty folder to make
sure it is properly detected as deleted in subsequent requests.
This works around a problem with phpseclib where the folder is properly
deleted remotely but the stat cache was not updated.
