Allow RDNS itself to be set as outbound proxy for other apps or VPN clients (daisy-chain rdns)

[onetimecontributor]

Disclaimer: I understand this is kinda niche request, though maybe it's not a big deal.

As RDNS is a great and (seems) unique tool that combines vpn client, on-device blocklists, upstream DNS etc, it may be useful to allow to set it as outbound proxy for either other apps or other VPN clients. Similar to how Orbot exposes it's services via HTTPS/SOCKS ports so rdns can use it as an upstream proxy.

What's expected to be shared: on-device blocklists, upstream DNS, VPN profiles (easiest - via the "routing default apps" vpn profile)

Cases where it may be useful:

• multiple user profiles (including work profiles) and Samsung's secured folder, so on a single device user can have 4 different profiles that currently requires configuration of 4x VPN profiles, 4x upstream DNS, 4x on-device blocklists. One can instead Install rdns in each profile with it's basic settings (or just app-specific allowlists) and chain-link them to the one instance that is fully configured with upstreams/vpns
• less relevant (providing Orbot-like feature "Open Proxy on All interfaces" is implemented), allow other devices connected to device's hotspot to be secured via rdns features in the similar way

[ignoramous]

The capability is there, but not exposed yet. Mostly because we don't have the time to support it. Need to get WireGuard specific stuff stable first.

Similar request for DNS:

• DoH Server #1603