fix: retry GitHub webhook delivery on 401 or missing secret

When a workflow is activated, n8n generates a new webhook secret in
staticData. If unihook's periodic refresh hasn't picked it up yet,
the first forward will fail (401 wrong HMAC, or no secret to sign with).

Changes:
- forward_event now returns the HTTP status code (Result<u16, ...>)
- forward_to_webhook returns Option<u16> for callers to inspect
- GitHubRouter::route_event implements a 3-phase retry:
  1. Forward to all matching triggers, collecting results
  2. Identify failures (401 or missing webhook secret)
  3. Refresh trigger cache from n8n API and retry failed deliveries
- Fix nginx mock regex to allow empty owner/repo segments (n8n sends
  POST /repos///hooks during initial workflow save)
- Add wiremock-based unit tests for retry logic:
  - test_no_retry_when_all_forwards_succeed
  - test_retry_on_401_refreshes_triggers_and_retries
  - test_retry_on_missing_secret_refreshes_and_retries

Bump to v0.3.1

Author: JonnyPower

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "n8n-slack-unihook"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2024"
 description = "A Slack event router for n8n that enables multiple workflows to share a single Slack app webhook"
 license = "MIT"
@@ -45,6 +45,8 @@ reqwest = { version = "0.13", features = ["json", "cookies"] }
 hmac = "0.12"
 sha2 = "0.10"
 hex = "0.4"
+# Mock HTTP server for unit tests
+wiremock = "0.6"
 
 [[test]]
 name = "integration"

src/n8n/client.rs

@@ -147,6 +147,7 @@ impl N8nClient {
                             events = ?trigger.events,
                             owner = %trigger.owner,
                             repository = %trigger.repository,
+                            has_webhook_secret = trigger.webhook_secret.is_some(),
                             "Found GitHub trigger"
                         );
                         triggers.push(trigger);
@@ -215,12 +216,15 @@ impl N8nClient {
     /// The `raw_body` parameter is the exact raw request body from the source
     /// (Slack, Jira, etc.). This is forwarded as-is (not re-serialized) to
     /// preserve the exact bytes for signature/authentication verification by n8n.
+    ///
+    /// Returns the HTTP status code from n8n's response on success, or an error
+    /// if the request couldn't be sent at all (connection failure, DNS, etc.).
     pub async fn forward_event(
         &self,
         webhook_url: &str,
         raw_body: &str,
         headers: &HeaderMap,
-    ) -> Result<(), N8nClientError> {
+    ) -> Result<u16, N8nClientError> {
         debug!(
             webhook_url = %webhook_url,
             forwarded_headers = headers.len(),
@@ -249,16 +253,18 @@ impl N8nClient {
             N8nClientError::RequestFailed(e.to_string())
         })?;
 
-        if !response.status().is_success() {
-            let status = response.status();
+        let status = response.status();
+        let status_code = status.as_u16();
+
+        if !status.is_success() {
             warn!(
                 status = %status,
                 webhook_url = %webhook_url,
                 "Webhook returned non-success status"
             );
         }
 
-        Ok(())
+        Ok(status_code)
     }
 }