- This commit contains initial support for uploading and sending images natively
-- i.e. a WhatsApp image upload, instead of sending through a bare link.
- All images supported by the OPTICL library are supported; this is because WA
needs us to generate a jpeg thumbnail for the image (which can probably be
made smaller)
- Importantly, this functionality is currently a trivial DoS vector: simply send
a large file (or an infinite file, like time.gif) and it ALL gets downloaded
and buffered into RAM...!
- At least this is limited to users who have actually registered with the
bridge.
- Failing to send the image in any way results in an XMPP error getting reported
back to the sender.
- Also, the initial registration QR code upload thing now happens in another
thread.
