[#2924549] feat: Invoke hook after a site install is complete

By: borisson_ By: Zuhal By: dawehner By: brooke_heaton By: twfahey By: catch By: alexpott By: godotislate By: rachel_norfolk By: Crell By: mile23 By: saltednut By: jhedstrom By: bircher By: andypost By: hardik_patel_12 By: loopy1492 By: vsujeetkumar By: simonbaese By: ankithashetty By: askibinski By: mlncn By: sandboxpl By: aneek By: samuel.mortenson By: joseph.olstad By: abhinand gokhala k By: david.radoc By: pooja saraah By: cmd87