An agency may:
1. Make covenants other than and in addition to the covenants expressly authorized of like or different character.
2. Make such covenants and do any and all such acts and things as may be necessary, convenient or desirable to secure its bonds, or, except as otherwise provided in this chapter, as will tend to make the bonds more marketable notwithstanding that such covenants, acts or things may not be enumerated in this chapter.