wire up loading of secretsmanager plugin, using renderer plugin as a model

pkg/plugins/manager/loader/initializer/initializer_test.go

@@ -79,6 +79,36 @@ func TestInitializer_Initialize(t *testing.T) {
 		assert.NotNil(t, c)
 	})
 
+	t.Run("secretsmanager", func(t *testing.T) {
+		p := &plugins.Plugin{
+			JSONData: plugins.JSONData{
+				ID:   "test",
+				Type: plugins.SecretsManager,
+				Dependencies: plugins.Dependencies{
+					GrafanaVersion: ">=8.x",
+				},
+				Backend: true,
+			},
+			PluginDir: absCurPath,
+			Class:     plugins.External,
+		}
+
+		i := &Initializer{
+			cfg: plugins.NewCfg(),
+			log: log.NewNopLogger(),
+			backendProvider: &fakeBackendProvider{
+				plugin: p,
+			},
+		}
+
+		err := i.Initialize(context.Background(), p)
+		assert.NoError(t, err)
+
+		c, exists := p.Client()
+		assert.True(t, exists)
+		assert.NotNil(t, c)
+	})
+
 	t.Run("non backend plugin app", func(t *testing.T) {
 		p := &plugins.Plugin{
 			JSONData: plugins.JSONData{