Alerting: Various fixes for the alerts endpoint (#33182)

A set of fixes for the GET alert and groups endpoints.

- First, is the fact that the default values where not being for the query params. I've introduced a new method in the Grafana context that allow us to do this.
- Second, is the fact that alerts were never being transitioned to active. To my surprise this is actually done by the inhibitor in the pipeline - if an alert is not muted, or inhibited then it's active.
- Third, I have added an integration test to cover for regressions.

Signed-off-by: Josue Abreu <josue@grafana.com>

pkg/models/context_test.go

@@ -0,0 +1,41 @@
+package models
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gopkg.in/macaron.v1"
+)
+
+func TestQueryBoolWithDefault(t *testing.T) {
+	tc := map[string]struct {
+		url          string
+		defaultValue bool
+		expected     bool
+	}{
+		"with no value specified, the default value is returned": {
+			url:          "http://localhost/api/v2/alerts",
+			defaultValue: true,
+			expected:     true,
+		},
+		"with a value specified, the default value is overridden": {
+			url:          "http://localhost/api/v2/alerts?silenced=false",
+			defaultValue: true,
+			expected:     false,
+		},
+	}
+
+	for name, tt := range tc {
+		t.Run(name, func(t *testing.T) {
+			req, err := http.NewRequest("GET", tt.url, nil)
+			require.NoError(t, err)
+			r := ReqContext{
+				Context: &macaron.Context{
+					Req: macaron.Request{Request: req},
+				},
+			}
+			require.Equal(t, tt.expected, r.QueryBoolWithDefault("silenced", tt.defaultValue))
+		})
+	}
+}