feature: passing client name to upstream server

[sweepies]

I'm using Blocky as a proxy to NextDNS for its web UI management and analytics visualization. I have configured clients to connect directly over DoH where possible, but for other devices I'd like to have Blocky forward the resolved client name (via rDNS) to the upstream.

For example, NextDNS expects it in the format of
https://dns.nextdns.io/<config_id>/<client_name> for DoH
<client_name>-<config_id>.dns.nextdns.io for DoT

I imagine the most reasonable way of doing this for wide compatibility would be a special placeholder in the upstream URL, like so:

upstream:
  default:
    - https://dns.nextdns.io/foo/${client_name}
    - ${client_name}-foo.dns.nextdns.io

[0xERR0R]

Client can have multiple names, in this case only the first should be used

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[github-actions]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 5 days.