(a) In all proceedings under this article between parents, it shall be expressly permissible for the parents of a minor child to present to the court an agreement respecting any and all issues concerning custody of the minor child. As used in this Code section, the term "custody" shall include, without limitation, joint custody as such term is defined in Code Section 19-9-6. As used in this Code section, the term "custody" shall not include payment of child support.

(b) The court shall ratify the agreement and make such agreement a part of the court's final judgment in the proceedings unless the court makes specific written factual findings as a part of the final judgment that under the circumstances of the parents and the child in such agreement that the agreement would not be in the best interests of the child. The court shall not refuse to ratify such agreement and to make such agreement a part of the final judgment based solely upon the parents' choice to use joint custody as a part of such agreement.

(c) In its judgment, the court may supplement the agreement on issues not covered by such agreement.