feat(alerting): custom alert support endpoint errors (#844)

* feat(alerting): add support for including endpoint errors in custom alerts

- Updated `buildHTTPRequest` method in `AlertProvider` to accept a `result` parameter.
- Added support for including `[ENDPOINT_ERRORS]` in both the request body and URL, which will be replaced by the errors from `Result.Errors[]`.
- Adjusted `CreateExternalEndpointResult` to capture and store errors from query parameters.
- This allows custom alerts to include detailed error information, enhancing the flexibility of alert notifications.

* feat: add ENDPOINT_ERRORS example

* feat: add tests

* Refactor: code review feedback

* delete unsed errors

* Update README.md

* Apply suggestions from code review

---------

Co-authored-by: raojinlin <raojinlin302@gmail.com>
Co-authored-by: TwiN <twin@linux.com>

api/external_endpoint.go

@@ -46,6 +46,9 @@ func CreateExternalEndpointResult(cfg *config.Config) fiber.Handler {
 			Success:   c.QueryBool("success"),
 			Errors:    []string{},
 		}
+		if !result.Success && c.Query("error") != "" {
+			result.Errors = append(result.Errors, c.Query("error"))
+		}
 		convertedEndpoint := externalEndpoint.ToEndpoint()
 		if err := store.Get().Insert(convertedEndpoint, result); err != nil {
 			if errors.Is(err, common.ErrEndpointNotFound) {

api/external_endpoint_test.go

@@ -76,6 +76,12 @@ func TestCreateExternalEndpointResult(t *testing.T) {
 			AuthorizationHeaderBearerToken: "Bearer token",
 			ExpectedCode:                   200,
 		},
+		{
+			Name:                           "good-token-success-true-with-ignored-error-because-success-true",
+			Path:                           "/api/v1/endpoints/g_n/external?success=true&error=failed",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   200,
+		},
 		{
 			Name:                           "good-token-success-false",
 			Path:                           "/api/v1/endpoints/g_n/external?success=false",
@@ -88,6 +94,12 @@ func TestCreateExternalEndpointResult(t *testing.T) {
 			AuthorizationHeaderBearerToken: "Bearer token",
 			ExpectedCode:                   200,
 		},
+		{
+			Name:                           "good-token-success-false-with-error",
+			Path:                           "/api/v1/endpoints/g_n/external?success=false&error=failed",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   200,
+		},
 	}
 	for _, scenario := range scenarios {
 		t.Run(scenario.Name, func(t *testing.T) {
@@ -114,21 +126,33 @@ func TestCreateExternalEndpointResult(t *testing.T) {
 		if endpointStatus.Key != "g_n" {
 			t.Errorf("expected key to be g_n but got %s", endpointStatus.Key)
 		}
-		if len(endpointStatus.Results) != 3 {
+		if len(endpointStatus.Results) != 5 {
 			t.Errorf("expected 3 results but got %d", len(endpointStatus.Results))
 		}
 		if !endpointStatus.Results[0].Success {
 			t.Errorf("expected first result to be successful")
 		}
-		if endpointStatus.Results[1].Success {
-			t.Errorf("expected second result to be unsuccessful")
+		if !endpointStatus.Results[1].Success {
+			t.Errorf("expected second result to be successful")
+		}
+		if len(endpointStatus.Results[1].Errors) > 0 {
+			t.Errorf("expected second result to have no errors")
 		}
 		if endpointStatus.Results[2].Success {
 			t.Errorf("expected third result to be unsuccessful")
 		}
+		if endpointStatus.Results[3].Success {
+			t.Errorf("expected fourth result to be unsuccessful")
+		}
+		if endpointStatus.Results[4].Success {
+			t.Errorf("expected fifth result to be unsuccessful")
+		}
+		if len(endpointStatus.Results[4].Errors) == 0 || endpointStatus.Results[4].Errors[0] != "failed" {
+			t.Errorf("expected fifth result to have errors: failed")
+		}
 		externalEndpointFromConfig := cfg.GetExternalEndpointByKey("g_n")
-		if externalEndpointFromConfig.NumberOfFailuresInARow != 2 {
-			t.Errorf("expected 2 failures in a row but got %d", externalEndpointFromConfig.NumberOfFailuresInARow)
+		if externalEndpointFromConfig.NumberOfFailuresInARow != 3 {
+			t.Errorf("expected 3 failures in a row but got %d", externalEndpointFromConfig.NumberOfFailuresInARow)
 		}
 		if externalEndpointFromConfig.NumberOfSuccessesInARow != 0 {
 			t.Errorf("expected 0 successes in a row but got %d", externalEndpointFromConfig.NumberOfSuccessesInARow)