Add generic set type (#21408)

This PR adds a generic set type to get rid of maps used as sets.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/public/public_test.go

@@ -7,28 +7,23 @@ package public
 import (
 	"testing"
 
+	"code.gitea.io/gitea/modules/container"
+
 	"github.com/stretchr/testify/assert"
 )
 
 func TestParseAcceptEncoding(t *testing.T) {
 	kases := []struct {
 		Header   string
-		Expected map[string]bool
+		Expected container.Set[string]
 	}{
 		{
-			Header: "deflate, gzip;q=1.0, *;q=0.5",
-			Expected: map[string]bool{
-				"deflate": true,
-				"gzip":    true,
-			},
+			Header:   "deflate, gzip;q=1.0, *;q=0.5",
+			Expected: container.SetOf("deflate", "gzip"),
 		},
 		{
-			Header: " gzip, deflate, br",
-			Expected: map[string]bool{
-				"deflate": true,
-				"gzip":    true,
-				"br":      true,
-			},
+			Header:   " gzip, deflate, br",
+			Expected: container.SetOf("deflate", "gzip", "br"),
 		},
 	}