Client exit node capability

[DrNoCDN]

Is your feature request related to a problem? Please describe.
I'm wondering if it is currently possible to configure an exit node on a client either via labels or another method. I couldn't find anything in the documentation that mentioned this.

Describe the solution you'd like
A simple configuration option for setting exit node for TSDproxy onboarded clients.

Describe alternatives you've considered
Thinking about internet egress secure traffic and how that compares with the usage of a VPN-based container (ie gluetun), the only other option is using dockers network_mode: "service:container". I'd prefer using a configured exit node as this is not host specific and could centralize the internet egress traffic.

Additional context
None

[DrNoCDN]

Noticed this is a duplicate request of #189, however I don't see any author/contributor responses there