feat(NIP-42): pubkey authentication

Configurable in `config.toml`.  Limited functionality, but this does
send metadata to gRPC for event authorization.

fixes: https://todo.sr.ht/~gheartsfield/nostr-rs-relay/66

src/nauthz.rs

@@ -76,6 +76,7 @@ impl EventAuthzService {
         origin: Option<String>,
         user_agent: Option<String>,
         nip05: Option<Nip05Name>,
+        auth_pubkey: Option<Vec<u8>>
     ) -> Result<Box<dyn AuthzDecision>> {
         self.ready_connection().await;
         let id_blob = hex::decode(&event.id)?;
@@ -97,7 +98,7 @@ impl EventAuthzService {
                     ip_addr: Some(ip.to_string()),
                     origin,
                     user_agent,
-                    auth_pubkey: None,
+                    auth_pubkey,
                     nip05: nip05.map(|x| nauthz_grpc::event_request::Nip05Name::from(x)),
                 })
                 .await?;