`DownloadableFileFilter` is an abstraction of the filtering we do in most of the `TorrentClient`s.
It operates on a single file at a time, not the entire torrent.
Tests:
- `GetDownloadLinks`
- `IncludeRegex` filter works
- `ExcludeRegex` filter works
- `DownloadMinSize` filter works
- only `IncludeRegex` is used when both `IncludeRegex` and `ExcludeRegex` are set
- gets links for all files if none of the above filters are set
- returns null if `torrent.RdId` is null
- `GetTorrents`
- [Both full/partial sync] returns empty list when no torrents present in api response
- [full sync] overrides any previous torrents in cache, deleting those not present in the api response
- [partial sync] updates torrents in cache according to the api response
- [partial sync] adds torrents to cache according to the api response
- `Map` (private so tested via `GetTorrents`)
- Computes progress correctly from `Downloaded / Size`
- `UpdateData`
- [`torrentClientTorrent != null`] does not get from api, updates the `torrent` accordingly
- [`torrentClientTorrent == null`] gets from api, updates the `torrent` accordingly
- [`torrentClientTorrent == null`] when torrent deleted from rd, updates `RdStatusRaw = "deleted""`
- when `torrent.RdId == null`, returns the `torrent` unmodified
Tests:
- [Both overloads] uses the `download.Link` to guess the filenamem if it's not present
- [Both overloads] returns null if `download.Link` is null
- [Both overloads] returns nuyll if `download.RdName` is null
- [Both overloads] works for a file in a deeply nested subdirectory
- [overload with `downloadPath` argument only] creates the correct directory
Tests:
- Downloads successfully when everything goes right first time
- Downloads successfully when the 5th api call is successful after 4 failures
- Fails to download when 5 api calls fail in a row
- Fails to download if the file has already been added to `Download Station` (when `GetInfoAsync` does not error)
- FAils to download if `remotePath` cannot be parsed by `Path.GetDirectoryName()`
