feat: Implement push-based external endpoints (#724)

* refactor: Move SSH outside of endpoint.go
* refactor: Use pointers for Alert receivers
* feat: Implement push-based external endpoints
* Fix failing tests
* Validate external endpoints on start
* Add tests for external endpoints
* refactor some error equality checks
* Improve docs and refactor some code
* Fix UI-related issues with external endpoints

api/external_endpoint_test.go

@@ -0,0 +1,131 @@
+package api
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/TwiN/gatus/v5/alerting"
+	"github.com/TwiN/gatus/v5/alerting/alert"
+	"github.com/TwiN/gatus/v5/alerting/provider/discord"
+	"github.com/TwiN/gatus/v5/config"
+	"github.com/TwiN/gatus/v5/config/maintenance"
+	"github.com/TwiN/gatus/v5/core"
+	"github.com/TwiN/gatus/v5/storage/store"
+	"github.com/TwiN/gatus/v5/storage/store/common/paging"
+)
+
+func TestCreateExternalEndpointResult(t *testing.T) {
+	defer store.Get().Clear()
+	defer cache.Clear()
+	cfg := &config.Config{
+		Alerting: &alerting.Config{
+			Discord: &discord.AlertProvider{},
+		},
+		ExternalEndpoints: []*core.ExternalEndpoint{
+			{
+				Name:  "n",
+				Group: "g",
+				Token: "token",
+				Alerts: []*alert.Alert{
+					{
+						Type:             alert.TypeDiscord,
+						FailureThreshold: 2,
+						SuccessThreshold: 2,
+					},
+				},
+			},
+		},
+		Maintenance: &maintenance.Config{},
+	}
+	api := New(cfg)
+	router := api.Router()
+	scenarios := []struct {
+		Name                           string
+		Path                           string
+		AuthorizationHeaderBearerToken string
+		ExpectedCode                   int
+	}{
+		{
+			Name:                           "no-token",
+			Path:                           "/api/v1/endpoints/g_n/external?success=true",
+			AuthorizationHeaderBearerToken: "",
+			ExpectedCode:                   401,
+		},
+		{
+			Name:                           "bad-token",
+			Path:                           "/api/v1/endpoints/g_n/external?success=true",
+			AuthorizationHeaderBearerToken: "Bearer bad-token",
+			ExpectedCode:                   401,
+		},
+		{
+			Name:                           "bad-key",
+			Path:                           "/api/v1/endpoints/bad_key/external?success=true",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   404,
+		},
+		{
+			Name:                           "good-token-success-true",
+			Path:                           "/api/v1/endpoints/g_n/external?success=true",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   200,
+		},
+		{
+			Name:                           "good-token-success-false",
+			Path:                           "/api/v1/endpoints/g_n/external?success=false",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   200,
+		},
+		{
+			Name:                           "good-token-success-false-again",
+			Path:                           "/api/v1/endpoints/g_n/external?success=false",
+			AuthorizationHeaderBearerToken: "Bearer token",
+			ExpectedCode:                   200,
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run(scenario.Name, func(t *testing.T) {
+			request := httptest.NewRequest("POST", scenario.Path, http.NoBody)
+			if len(scenario.AuthorizationHeaderBearerToken) > 0 {
+				request.Header.Set("Authorization", scenario.AuthorizationHeaderBearerToken)
+			}
+			response, err := router.Test(request)
+			if err != nil {
+				return
+			}
+			defer response.Body.Close()
+			if response.StatusCode != scenario.ExpectedCode {
+				t.Errorf("%s %s should have returned %d, but returned %d instead", request.Method, request.URL, scenario.ExpectedCode, response.StatusCode)
+			}
+		})
+	}
+	t.Run("verify-end-results", func(t *testing.T) {
+		endpointStatus, err := store.Get().GetEndpointStatus("g", "n", paging.NewEndpointStatusParams().WithResults(1, 10))
+		if err != nil {
+			t.Errorf("failed to get endpoint status: %s", err.Error())
+			return
+		}
+		if endpointStatus.Key != "g_n" {
+			t.Errorf("expected key to be g_n but got %s", endpointStatus.Key)
+		}
+		if len(endpointStatus.Results) != 3 {
+			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[2].Success {
+			t.Errorf("expected third result to be unsuccessful")
+		}
+		externalEndpointFromConfig := cfg.GetExternalEndpointByKey("g_n")
+		if externalEndpointFromConfig.NumberOfFailuresInARow != 2 {
+			t.Errorf("expected 2 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)
+		}
+	})
+}