feat: Support for custom osk (output key) domain separators in Rosenpass app

This allows for custom protocol extensions with custom domain
separators to be used without modifying the Rosenpass source code

rp/src/exchange.rs

@@ -208,7 +208,10 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
     use rosenpass::{
         app_server::{AppServer, BrokerPeer},
         config::Verbosity,
-        protocol::basic_types::{SPk, SSk, SymKey},
+        protocol::{
+            basic_types::{SPk, SSk, SymKey},
+            osk_domain_separator::OskDomainSeparator,
+        },
     };
     use rosenpass_secret_memory::Secret;
     use rosenpass_util::file::{LoadValue as _, LoadValueB64};
@@ -362,6 +365,7 @@ pub async fn exchange(options: ExchangeOptions) -> Result<()> {
             broker_peer,
             peer.endpoint.map(|x| x.to_string()),
             peer.protocol_version,
+            OskDomainSeparator::for_wireguard_psk(),
         )?;
 
         // Configure routes, equivalent to `ip route replace <allowed_ips> dev <dev>` and set up