A person interested as or through an executor, administrator, trustee, guardian, or other fiduciary, creditor, devisee, legatee, heir, next of kin, or cestui que trust, in the administration of a trust, or of the estate of a decedent, an infant, lunatic, or insolvent, may have a declaration of rights or legal relations in respect thereto:
La. C.P. ยง 1874