fix(middleware): improve error reporting and logging

- Add detailed error logging in attestation middleware
- Enhance signer middleware with better error reporting
- Improve error responses with structured JSON format
- Maintain backward compatibility with existing behavior
- Add tests for error handling scenarios

This change addresses debugging challenges by adding proper tracing
while preserving the original middleware behavior.

Author: neithanmo

crates/service/src/error.rs

@@ -40,18 +40,19 @@ pub enum IndexerServiceError {
 // Helper struct to properly format
 // error messages
 #[derive(Serialize)]
-struct ErrorResponse {
-    message: String,
+#[cfg_attr(test, derive(serde::Deserialize))]
+pub struct ErrorResponse {
+    pub(crate) message: String,
 }
 
 impl ErrorResponse {
-    fn new(message: impl ToString) -> Self {
+    pub fn new(message: impl ToString) -> Self {
         Self {
             message: message.to_string(),
         }
     }
 
-    fn into_response(self, status_code: StatusCode) -> Response {
+    pub fn into_response(self, status_code: StatusCode) -> Response {
         (status_code, Json(self)).into_response()
     }
 }

crates/service/src/middleware/attestation.rs

@@ -14,7 +14,7 @@ use reqwest::StatusCode;
 use serde::Serialize;
 use thegraph_core::attestation::Attestation;
 
-use crate::error::StatusCodeExt;
+use crate::error::{ErrorResponse, StatusCodeExt};
 
 #[derive(Clone)]
 pub enum AttestationInput {
@@ -56,6 +56,11 @@ pub async fn attestation_middleware(
         (Some(signer), Some(AttestationInput::Attestable { req })) => {
             Some(signer.create_attestation(req, &res))
         }
+        (None, Some(AttestationInput::Attestable { .. })) => {
+            // keep this branch separated just to log the missing signer condition
+            tracing::warn!("Attestation requested but no signer found");
+            None
+        }
         _ => None,
     };
 
@@ -93,12 +98,14 @@ impl StatusCodeExt for AttestationError {
 
 impl IntoResponse for AttestationError {
     fn into_response(self) -> Response {
-        self.status_code().into_response()
+        tracing::error!("Attestation error: {}", self);
+        let status_code = self.status_code();
+        ErrorResponse::new(self).into_response(status_code)
     }
 }
 
 #[cfg(test)]
-mod tests {
+mod attestation_tests {
     use axum::{
         body::{to_bytes, Body},
         http::{Request, Response},

crates/service/src/middleware/attestation_signer.rs

@@ -30,6 +30,12 @@ pub async fn signer_middleware(
     if let Some(Allocation(allocation_id)) = request.extensions().get::<Allocation>() {
         if let Some(signer) = state.attestation_signers.borrow().get(allocation_id) {
             request.extensions_mut().insert(signer.clone());
+        } else {
+            // Just log this case which is silently passed through next middleware
+            tracing::warn!(
+                "No attestation signer found for allocation {}",
+                allocation_id
+            );
         }
     }