AlertingNG: base API implementation (#31824)

* AlertingNG: base API implementation

* Pass the interface instead of the base impl

* Ruler mock draft (WIP)

* Update alerting-api dependency

* Improve mock implementation

pkg/services/ngalert/api/util_test.go

@@ -0,0 +1,27 @@
+package api
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestToMacaronPath(t *testing.T) {
+	testCases := []struct {
+		inputPath          string
+		expectedOutputPath string
+	}{
+		{
+			inputPath:          "",
+			expectedOutputPath: "",
+		},
+		{
+			inputPath:          "/ruler/{DatasourceId}/api/v1/rules/{Namespace}/{Groupname}",
+			expectedOutputPath: "/ruler/:DatasourceId/api/v1/rules/:Namespace/:Groupname",
+		},
+	}
+	for _, tc := range testCases {
+		outputPath := toMacaronPath(tc.inputPath)
+		assert.Equal(t, tc.expectedOutputPath, outputPath)
+	}
+}