Circling back here after fighting with Thunderbird for a few days:

> Slidge will not let you do that. One slidge account=one bare JID, and 
> there's no way of "legacy multi accounting" with a single JID. I you 
> really want to do that, just create another JID? Gajim, Dino, 
> Conversations [...] all allow XMPP multi accounts in a unified view.
> [...]
> I don't think so, but clients *could*. Another XMPP account/JID sounds 
> like a reasonable option if you really want to multi legacy account 
> with slidge. I guess we could do something based on the resource if we 
> really wanted it, but I am not sure it's worth the added complexity. 
> Is that something you need? 
That makes sense -- I think I misunderstood how multi-device linking 
works for Signal, and thought you were able to link multiple devices

Thanks for the thorough review! Even in beta, Slidge is awesome.
> Supposedly, contacts are bound to a unique session instance, and thus 
> are never shared between different sessions. They are discriminated by 
> the stanzas "from" attribute and dispatched to the appropriate session 
> (see `BaseGateway.__register_handlers()`). I might be missing 
> something here; have you witnessed some sort of leaking between 
> different sessions?

My understanding is that, since each session can populate the XMPP 
account's roster individually and there's no way of differentiating 
between the "source" session or account for a legacy contact in XMPP, 
it's unclear how a user might choose to send a message from one account 
or the other.

This commit implements basic support for WhatsApp via the multi-device
API, as supported by the `tulir/whatsmeow` Go library. Integration
between Python and Go has been achieved using GoPy, but the artifacts
produced are not (yet) commited to the repository; the Docker development
environment has been configured to build (and re-build) these as needed,
but local development remains an open question.

Most features currently supported within Slidge are also supported by
the WhatsApp plugin, with the notable omission of message correction,
which is currently unsupported by WhatsApp itself (but see here[0] for
more). Feature parity will continue to evolve as Slidge evolves.

Even so, there are several caveats or missing pieces to this work, e.g.:
[message trimmed]

This commit implements basic support for WhatsApp via the multi-device
API, as supported by the `tulir/whatsmeow` Go library. Integration
between Python and Go has been achieved using GoPy, but the artifacts
produced are not (yet) commited to the repository; the Docker development
environment has been configured to build (and re-build) these as needed,
but local development remains an open question.

Most features currently supported within Slidge are also supported by
the WhatsApp plugin, with the notable omission of message correction,
which is currently unsupported by WhatsApp itself (but see here[0] for
more). Feature parity will continue to evolve as Slidge evolves.

Even so, there are several caveats or missing pieces to this work, e.g.:
[message trimmed]