Outline the Ethereum processor

This was only half-finished to begin with, unfortunately...

processor/ethereum/src/publisher.rs

@@ -0,0 +1,60 @@
+use core::future::Future;
+
+use crate::transaction::Transaction;
+
+#[derive(Clone)]
+pub(crate) struct TransactionPublisher {
+  relayer_url: String,
+}
+
+impl TransactionPublisher {
+  pub(crate) fn new(relayer_url: String) -> Self {
+    Self { relayer_url }
+  }
+}
+
+impl signers::TransactionPublisher<Transaction> for TransactionPublisher {
+  type EphemeralError = ();
+
+  fn publish(
+    &self,
+    tx: Transaction,
+  ) -> impl Send + Future<Output = Result<(), Self::EphemeralError>> {
+    async move {
+      /*
+      use tokio::{
+        io::{AsyncReadExt, AsyncWriteExt},
+        net::TcpStream,
+      };
+
+      let mut msg = vec![];
+      match completion.command() {
+        RouterCommand::UpdateSeraiKey { nonce, .. } | RouterCommand::Execute { nonce, .. } => {
+          msg.extend(&u32::try_from(nonce).unwrap().to_le_bytes());
+        }
+      }
+      completion.write(&mut msg).unwrap();
+
+      let Ok(mut socket) = TcpStream::connect(&self.relayer_url).await else {
+        log::warn!("couldn't connect to the relayer server");
+        Err(NetworkError::ConnectionError)?
+      };
+      let Ok(()) = socket.write_all(&u32::try_from(msg.len()).unwrap().to_le_bytes()).await else {
+        log::warn!("couldn't send the message's len to the relayer server");
+        Err(NetworkError::ConnectionError)?
+      };
+      let Ok(()) = socket.write_all(&msg).await else {
+        log::warn!("couldn't write the message to the relayer server");
+        Err(NetworkError::ConnectionError)?
+      };
+      if socket.read_u8().await.ok() != Some(1) {
+        log::warn!("didn't get the ack from the relayer server");
+        Err(NetworkError::ConnectionError)?;
+      }
+
+      Ok(())
+      */
+      todo!("TODO")
+    }
+  }
+}