@UnstableApi
    public Endpoint withDefaultPort(SessionProtocol protocol) {
        requireNonNull(protocol, "protocol");
        return withDefaultPort(protocol.defaultPort());
    }
Returns a new host endpoint with the default port number of the specified {@link SessionProtocol}.

@param protocol the {@link SessionProtocol} that will provide the default port number
@return the new endpoint whose port is the default port number of the specified
        {@link SessionProtocol} if this endpoint does not have its port specified.
        {@code this} if this endpoint already has its port specified.
core/src/main/java/com/linecorp/armeria/client/Endpoint.java