feat: update swagger api json with tags (#347)

Signed-off-by: Товарищ программист <2962928213@qq.com>

controllers/base.go

@@ -21,10 +21,16 @@ import (
 	"github.com/casbin/casdoor/util"
 )
 
+// controller for handlers under /api uri
 type ApiController struct {
 	beego.Controller
 }
 
+// controller for handlers directly under / (root)
+type RootController struct {
+	ApiController
+}
+
 type SessionData struct {
 	ExpireTime int64
 }