This PR adds support for using Box, Dropbox, GoogleDrive, SharepointV2, MicrosoftGroups, and OneDrive as remote sources.
For GoogleDrive, this requires full permissions and not just the regular OAuth access token.
Also extended S3 and SMB to actually look up a file if requested, which makes it possible to rely on the backup exclusion files, even when using remote sources. (SSH/SFTP does not currently support this).
This PR updates existing backends to implement the `IRenameEnabledBackend` interface, allowing for more efficient file renaming operations. The implementation varies by backend, with some using native rename operations and others falling back to copy-and-delete patterns.
This PR adds a dynamic property so a backend can signal if it supports streaming, based on the settings.
This is currently used for the File backend, so that toggling `--use-move-for-put` will disable streaming on the backend instead of relying on the `--disable-streaming-transfers` flag.
This PR moves the check from the FTP backend into shared code, so all backends will now check for read/write permissions when using the "Test" button.
For situations where write permissions are not required (like restore or verify) there is a flag on the v2 API that indicates if the connection was established, so the UI can show a message suggesting that it is possible to proceed, if the current UI operation does not require write permissions.
This fixes#2473
