This is the last part of unix socket support to talk to app servers, go
based app services already support unix sockets:
5a68173fe3
```
appservice:
# The address that the homeserver can use to connect to this appservice.
address: unix:///var/snap/matrix/current/whatsapp.socket
# The hostname and port where this appservice should listen.
hostname: /var/snap/matrix/current/whatsapp.socket
port: 0
```
### Pull Request Checklist
<!-- Please read
https://matrix-org.github.io/dendrite/development/contributing before
submitting your pull request -->
* [x] I have added Go unit tests or [Complement integration
tests](https://github.com/matrix-org/complement) for this PR _or_ I have
justified why this PR doesn't need tests
* [x] Pull request includes a [sign off below using a legally
identifiable
name](https://matrix-org.github.io/dendrite/development/contributing#sign-off)
_or_ I have already signed off privately
Signed-off-by: `Boris Rybalkin <ribalkin@gmail.com>`
985298cfc4