Store and use seconds for timeline time comments (#25392)

this will allow us to fully localize it later

PS: we can not migrate back as the old value was a one-way conversion


prepare for  #25213

---
*Sponsored by Kithara Software GmbH*

services/convert/issue_comment.go

@@ -11,6 +11,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/log"
 	api "code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/util"
 )
 
 // ToComment converts a issues_model.Comment to the api.Comment format
@@ -66,6 +67,17 @@ func ToTimelineComment(ctx context.Context, c *issues_model.Comment, doer *user_
 		return nil
 	}
 
+	if c.Content != "" {
+		if (c.Type == issues_model.CommentTypeAddTimeManual ||
+			c.Type == issues_model.CommentTypeStopTracking ||
+			c.Type == issues_model.CommentTypeDeleteTimeManual) &&
+			c.Content[0] == '|' {
+			// TimeTracking Comments from v1.21 on store the seconds instead of an formated string
+			// so we check for the "|" delimeter and convert new to legacy format on demand
+			c.Content = util.SecToTime(c.Content[1:])
+		}
+	}
+
 	comment := &api.TimelineComment{
 		ID:       c.ID,
 		Type:     c.Type.String(),