Support comma-delimited string as labels in issue template (#21831)

The [labels in issue YAML
templates](https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-issue-forms#top-level-syntax)
can be a string array or a comma-delimited string, so a single string
should be valid labels.

The old codes committed in #20987 ignore this, that's why the warning is
displayed:

<img width="618" alt="image"
src="https://user-images.githubusercontent.com/9418365/202112642-93dc72d0-71c3-40a2-9720-30fc2d48c97c.png">

Fixes #17877.

1 files changed, 26 insertions, 22 deletions

diff --git a/modules/markup/markdown/meta_test.go b/modules/markup/markdown/meta_test.go
index 720d0066f4..1e9768e618 100644
--- a/modules/markup/markdown/meta_test.go
+++ b/modules/markup/markdown/meta_test.go
@@ -9,82 +9,86 @@ import (
 	"strings"
 	"testing"
 
-	"code.gitea.io/gitea/modules/structs"
-
 	"github.com/stretchr/testify/assert"
 )
 
-func validateMetadata(it structs.IssueTemplate) bool {
-	/*
-		A legacy to keep the unit tests working.
-		Copied from the method "func (it IssueTemplate) Valid() bool", the original method has been removed.
-		Because it becomes quite complicated to validate an issue template which is support yaml form now.
-		The new way to validate an issue template is to call the Validate in modules/issue/template,
-	*/
+/*
+IssueTemplate is a legacy to keep the unit tests working.
+Copied from structs.IssueTemplate, the original type has been changed a lot to support yaml template.
+*/
+type IssueTemplate struct {
+	Name   string   `json:"name" yaml:"name"`
+	Title  string   `json:"title" yaml:"title"`
+	About  string   `json:"about" yaml:"about"`
+	Labels []string `json:"labels" yaml:"labels"`
+	Ref    string   `json:"ref" yaml:"ref"`
+}
+
+func (it *IssueTemplate) Valid() bool {
 	return strings.TrimSpace(it.Name) != "" && strings.TrimSpace(it.About) != ""
 }
 
 func TestExtractMetadata(t *testing.T) {
 	t.Run("ValidFrontAndBody", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		body, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s\n%s", sepTest, frontTest, sepTest, bodyTest), &meta)
 		assert.NoError(t, err)
 		assert.Equal(t, bodyTest, body)
 		assert.Equal(t, metaTest, meta)
-		assert.True(t, validateMetadata(meta))
+		assert.True(t, meta.Valid())
 	})
 
 	t.Run("NoFirstSeparator", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		_, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", frontTest, sepTest, bodyTest), &meta)
 		assert.Error(t, err)
 	})
 
 	t.Run("NoLastSeparator", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		_, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, bodyTest), &meta)
 		assert.Error(t, err)
 	})
 
 	t.Run("NoBody", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		body, err := ExtractMetadata(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, sepTest), &meta)
 		assert.NoError(t, err)
 		assert.Equal(t, "", body)
 		assert.Equal(t, metaTest, meta)
-		assert.True(t, validateMetadata(meta))
+		assert.True(t, meta.Valid())
 	})
 }
 
 func TestExtractMetadataBytes(t *testing.T) {
 	t.Run("ValidFrontAndBody", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		body, err := ExtractMetadataBytes([]byte(fmt.Sprintf("%s\n%s\n%s\n%s", sepTest, frontTest, sepTest, bodyTest)), &meta)
 		assert.NoError(t, err)
 		assert.Equal(t, bodyTest, string(body))
 		assert.Equal(t, metaTest, meta)
-		assert.True(t, validateMetadata(meta))
+		assert.True(t, meta.Valid())
 	})
 
 	t.Run("NoFirstSeparator", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		_, err := ExtractMetadataBytes([]byte(fmt.Sprintf("%s\n%s\n%s", frontTest, sepTest, bodyTest)), &meta)
 		assert.Error(t, err)
 	})
 
 	t.Run("NoLastSeparator", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		_, err := ExtractMetadataBytes([]byte(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, bodyTest)), &meta)
 		assert.Error(t, err)
 	})
 
 	t.Run("NoBody", func(t *testing.T) {
-		var meta structs.IssueTemplate
+		var meta IssueTemplate
 		body, err := ExtractMetadataBytes([]byte(fmt.Sprintf("%s\n%s\n%s", sepTest, frontTest, sepTest)), &meta)
 		assert.NoError(t, err)
 		assert.Equal(t, "", string(body))
 		assert.Equal(t, metaTest, meta)
-		assert.True(t, validateMetadata(meta))
+		assert.True(t, meta.Valid())
 	})
 }
 
@@ -97,7 +101,7 @@ labels:
   - bug
   - "test label"`
 	bodyTest = "This is the body"
-	metaTest = structs.IssueTemplate{
+	metaTest = IssueTemplate{
 		Name:   "Test",
 		About:  "A Test",
 		Title:  "Test Title",