Recent WhatsApp versions have begun allowing for message
correction/editing support; this commit integrates this official support
into pre-existing support for XEP-0308 (Message Correction) in Slidge.
Both incoming and outgoing message corrections are supported. However,
there are currently known issues with corrections made on own messages
in the official WhatsApp client, which are not reflected in XMPP
clients; these will be corrected in future commits.
nicoco
Alex Palaistras