Extract actions on new issue from models to services (#8217)

* extract actions on new issue from models to services

* improve code

* rename services/issues to services/issue

routers/api/v1/repo/issue.go

@@ -19,6 +19,7 @@ import (
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
+	issue_service "code.gitea.io/gitea/services/issue"
 	milestone_service "code.gitea.io/gitea/services/milestone"
 )
 
@@ -217,7 +218,7 @@ func CreateIssue(ctx *context.APIContext, form api.CreateIssueOption) {
 		form.Labels = make([]int64, 0)
 	}
 
-	if err := models.NewIssue(ctx.Repo.Repository, issue, form.Labels, assigneeIDs, nil); err != nil {
+	if err := issue_service.NewIssue(ctx.Repo.Repository, issue, form.Labels, assigneeIDs, nil); err != nil {
 		if models.IsErrUserDoesNotHaveAccessToRepo(err) {
 			ctx.Error(400, "UserDoesNotHaveAccessToRepo", err)
 			return