feat: enforce min bump in replacement messages

Author: MarcosNicolau

crates/batcher/src/lib.rs

@@ -1007,13 +1007,17 @@ impl Batcher {
             return;
         };
 
+        // the replacement max fee bump must be at least 10 percent higher
+        // TODO: move this to a config file
         let original_max_fee = entry.nonced_verification_data.max_fee;
-        if original_max_fee > replacement_max_fee {
+        let bump_factor_percentage = 10;
+        let min_bump = original_max_fee * U256::from(bump_factor_percentage) / U256::from(100);
+        if replacement_max_fee < min_bump {
             std::mem::drop(batch_state_lock);
             warn!("Invalid replacement message for address {addr}, had max fee: {original_max_fee:?}, received fee: {replacement_max_fee:?}");
             send_message(
                 ws_conn_sink.clone(),
-                SubmitProofResponseMessage::InvalidReplacementMessage,
+                SubmitProofResponseMessage::UnderpricedProof,
             )
             .await;
             self.metrics