(a)    The city council may, by ordinance, authorize the city manager to enter into agreements that require city contributions toward the cost of city public improvements to be constructed by developers or other persons.  These public improvements shall not be subject to the public improvement process set forth in this chapter.

    (b)    Any agreement with a developer or other person that requires the city to construct a public improvement shall be conditioned upon city council approval of the project in accordance with the public improvement process set forth in this chapter.