After the creation of a joint agency, another municipality may become a member of the joint agency upon application to the joint agency after the adoption of a resolution of the governing body of the municipality as prescribed in section 31 of this article authorizing the municipality to participate, and with the unanimous consent of the members of the joint agency as provided in section 34(6). A municipality may withdraw from a joint agency, except that all contractual rights acquired and obligations incurred while a member municipality remain in full force and effect.