feat: support group invite privacy verification

server/db/mysql/tenant_groups.go

@@ -499,6 +499,12 @@ func (a *adapter) TenantGroupInvitationAccept(id t.TenantID, invitationID string
 	if inv.Status == t.GroupInvitationStatusJoined || inv.Result == "joined" {
 		return &inv, nil
 	}
+	if strings.TrimSpace(inv.JoinRequestID) != "" {
+		if err = tx.Commit(); err != nil {
+			return nil, err
+		}
+		return &inv, nil
+	}
 	var deletedAt sql.NullTime
 	err = tx.QueryRowxContext(ctx, "SELECT deletedat FROM im_subscriptions WHERE topic=? AND userid=?",
 		inv.Topic, decodeUID(uid)).Scan(&deletedAt)