Support anonymous LDAP connections

Simply by setting an empty bind DN.

ldap/pool.go

@@ -40,10 +40,12 @@ func (p *ConnectionPool) connect(ctx context.Context) (*ldap.Conn, error) {
 	conn := ldap.NewConn(c, false)
 	conn.Start()
 
-	conn.SetTimeout(time.Until(deadline))
-	if _, err = conn.SimpleBind(ldap.NewSimpleBindRequest(p.bindDN, p.bindPw, nil)); err != nil {
-		conn.Close()
-		return nil, err
+	if p.bindDN != "" {
+		conn.SetTimeout(time.Until(deadline))
+		if _, err = conn.SimpleBind(ldap.NewSimpleBindRequest(p.bindDN, p.bindPw, nil)); err != nil {
+			conn.Close()
+			return nil, err
+		}
 	}
 
 	return conn, err