Allow bindaddress to be a unix socket

[2xsaiko]

Is your feature request related to a problem? Please describe.

It would be great if bindaddress in the server config could be a unix socket path in addition to an inet socket. Right now it gives this error message:

[error]: Failed to parse address ("unix:/var/run/kanidmd/web.sock") from config: AddrParseError(Socket)

I've also tried without the unix:, no idea if this is already possible and I just don't know the syntax.

Describe the solution you'd like

Allow setting e.g. bindaddress="unix:/var/run/kanidmd/web.sock"

Describe alternatives you've considered

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Additional context

I would like this mainly so I don't have to assign a unique port on localhost for an upstream for a reverse proxy.

[yaleman]

There's a lot more to it than just "put path in and bind" but yep, this is a feature we'll implement at some point.