Unix support for connecting to appservice

[realtyem]

Nothing to fancy, shouldn't need any configuration changes on either end(I think).

• Fixes Enable connecting to appservices through unix sockets #16399

I think the only thing of note is that for forming a request URI with a unix:// scheme, a : is appended to the end of the filename of the socket, to allow parsing out where the filename ends and the URL path begins(very similar to how Nginx does it). So:

• unix:/path/to.socket with a request to /_matrix/app/v1/ping

internally as it's passed into the request function will look like:

• unix:/path/to.socket:/_matrix/app/v1/ping.

Additionally, as a sanity check, the scheme can have multiple / between the unix: and the path to the socket file, as I've encountered multiple variants over the years(and there seems to be no real standard). So that means that if any of these will be stripped to a single / and look like the first item below:

• unix:/path/to.socket
• unix://path/to.socket
• unix:///path/to.socket

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file.
• Pull request includes a sign off
• Code style is correct
  (run the linters)

Signed-off-by: Jason Little realtyem@gmail.com