Fall back to room-less file URL format when parsing open group download URLs

[mpretty-cyro]

No description provided.

[jagerman]

The code seems fine, but I'm a little bit confused how this can actually work: do clients have to throw away most of the URL but keep the ID and then reconstruct the URL to actually download a file? As far as I know, sogs always requires the /room/NAME/file/N URL to get a room attachment.

[mpretty-cyro]

Yep pretty much, below are the Android and Desktop versions - they grab the last part of the url to get the fileId and then reconstruct the SOGS endpoint with that id so it doesn't actually matter what the downloadUrl is.

In the last major iOS release before we shut down I updated iOS to use open_group_server::parse_download_url which deconstructed the url into a structured object, but required it to be in the correct structure which, combined with the incorrect structure Android was generating (Fix), resulted in iOS failing to download community attachments sent from Android.

This change is to add support for the incorrect URL (so a future universal client is able to download images sent by the broken Android versions), and an update to iOS which has a similar fallback to extract the last part of the url if libSession fails to parse it.

Android:

val url = attachment.url.toHttpUrlOrNull()!!
val fileID = url.pathSegments.last()

communityApiExecutor.execute(
    CommunityApiRequest(
        serverBaseUrl = threadRecipient.address.serverUrl,
        api = communityFileDownloadApiFactory.create(
            room = threadRecipient.address.room,
            fileId = fileID,
            requiresSigning = true,
        )
    )
).toByteArraySlice()

Desktop:

export function attachmentIdAsStrFromUrl(fullUrl: string) {
  const url = new URL(fullUrl);
  const lastSegment = extractLastPathSegment(url);
  if (!lastSegment) {
    throw new Error('attachmentIdAsStrFromUrl last segment is not valid');
  }
  return lastSegment;
}