feat(alerting): Persist triggered alerts across application restart (#764)

* feat(alerting): Persist triggered alerts across application restart

Fixes #679

* test(alerting): Add numerous tests related to alerts

alerting/alert/alert_test.go

@@ -84,3 +84,109 @@ func TestAlert_IsSendingOnResolved(t *testing.T) {
 		t.Error("alert.IsSendingOnResolved() should've returned true, because SendOnResolved was set to true")
 	}
 }
+
+func TestAlert_Checksum(t *testing.T) {
+	description1, description2 := "a", "b"
+	yes, no := true, false
+	scenarios := []struct {
+		name     string
+		alert    Alert
+		expected string
+	}{
+		{
+			name: "barebone",
+			alert: Alert{
+				Type: TypeDiscord,
+			},
+			expected: "fed0580e44ed5701dbba73afa1f14b2c53ca5a7b8067a860441c212916057fe3",
+		},
+		{
+			name: "with-description-1",
+			alert: Alert{
+				Type:        TypeDiscord,
+				Description: &description1,
+			},
+			expected: "005f407ebe506e74a4aeb46f74c28b376debead7011e1b085da3840f72ba9707",
+		},
+		{
+			name: "with-description-2",
+			alert: Alert{
+				Type:        TypeDiscord,
+				Description: &description2,
+			},
+			expected: "3c2c4a9570cdc614006993c21f79a860a7f5afea10cf70d1a79d3c49342ef2c8",
+		},
+		{
+			name: "with-description-2-and-enabled-false",
+			alert: Alert{
+				Type:        TypeDiscord,
+				Enabled:     &no,
+				Description: &description2,
+			},
+			expected: "837945c2b4cd5e961db3e63e10c348d4f1c3446ba68cf5a48e35a1ae22cf0c22",
+		},
+		{
+			name: "with-description-2-and-enabled-true",
+			alert: Alert{
+				Type:        TypeDiscord,
+				Enabled:     &yes, // it defaults to true if not set, but just to make sure
+				Description: &description2,
+			},
+			expected: "3c2c4a9570cdc614006993c21f79a860a7f5afea10cf70d1a79d3c49342ef2c8",
+		},
+		{
+			name: "with-description-2-and-enabled-true-and-send-on-resolved-true",
+			alert: Alert{
+				Type:           TypeDiscord,
+				Enabled:        &yes,
+				SendOnResolved: &yes,
+				Description:    &description2,
+			},
+			expected: "bf1436995a880eb4a352c74c5dfee1f1b5ff6b9fc55aef9bf411b3631adfd80c",
+		},
+		{
+			name: "with-description-2-and-failure-threshold-7",
+			alert: Alert{
+				Type:             TypeSlack,
+				FailureThreshold: 7,
+				Description:      &description2,
+			},
+			expected: "8bd479e18bda393d4c924f5a0d962e825002168dedaa88b445e435db7bacffd3",
+		},
+		{
+			name: "with-description-2-and-failure-threshold-9",
+			alert: Alert{
+				Type:             TypeSlack,
+				FailureThreshold: 9,
+				Description:      &description2,
+			},
+			expected: "5abdfce5236e344996d264d526e769c07cb0d3d329a999769a1ff84b157ca6f1",
+		},
+		{
+			name: "with-description-2-and-success-threshold-5",
+			alert: Alert{
+				Type:             TypeSlack,
+				SuccessThreshold: 7,
+				Description:      &description2,
+			},
+			expected: "c0000e73626b80e212cfc24830de7094568f648e37f3e16f9e68c7f8ef75c34c",
+		},
+		{
+			name: "with-description-2-and-success-threshold-1",
+			alert: Alert{
+				Type:             TypeSlack,
+				SuccessThreshold: 1,
+				Description:      &description2,
+			},
+			expected: "5c28963b3a76104cfa4a0d79c89dd29ec596c8cfa4b1af210ec83d6d41587b5f",
+		},
+	}
+	for _, scenario := range scenarios {
+		t.Run(scenario.name, func(t *testing.T) {
+			scenario.alert.ValidateAndSetDefaults()
+			if checksum := scenario.alert.Checksum(); checksum != scenario.expected {
+				t.Errorf("expected checksum %v, got %v", scenario.expected, checksum)
+			}
+		})
+	}
+}