Add deprecated log when using MySQL with utf8 charset (go-gitea#19952)

Author: lunny

modules/setting/database.go

@@ -13,6 +13,8 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	"code.gitea.io/gitea/modules/log"
 )
 
 var (
@@ -83,6 +85,10 @@ func InitDBConfig() {
 	Database.Schema = sec.Key("SCHEMA").String()
 	Database.SSLMode = sec.Key("SSL_MODE").MustString("disable")
 	Database.Charset = sec.Key("CHARSET").In(defaultCharset, []string{"utf8", "utf8mb4"})
+	if Database.UseMySQL && defaultCharset != "utf8mb4" {
+		log.Error("Deprecated database mysql charset utf8 support, please use utf8mb4 or convert utf8 to utf8mb4.")
+	}
+
 	Database.Path = sec.Key("PATH").MustString(filepath.Join(AppDataPath, "gitea.db"))
 	Database.Timeout = sec.Key("SQLITE_TIMEOUT").MustInt(500)
 	Database.MaxIdleConns = sec.Key("MAX_IDLE_CONNS").MustInt(2)