[1243] Add equipment item notes only after reservations save

[orenyk]

Resolves #1243

• remove EquipmentItem#make_reservation_notes calls from Reservation
  methods
• only add equipment item notes once the relevant reservation has been
  saved to the database
• add specs for failed checkout / checkin to ensure that equipment item
  notes aren't saved
• improve current_user feature spec helper method
• fix N+1 query in the manage reservations view
• add exception handling to ReservationsController#archive

[AlanLiu96]

Checked it out! It works as expected now. Design wise though, it might improve workflow if not checking ToS would generate an alert that blocks the form from being submitted much like how not selecting a model generates an alert, instead of clearing the form and displaying an error flash.

[orenyk]

That's a good point, we could also make the ToS checkbox required for checkout requests. I'll go back into this branch and see how easy it is to implement.

[orenyk]

On looking into this further, there's no simple way to make a check_box_tag required without some JS and more complex front-end hackery. Given the hopeful rewrite to come, at some point, I don't think it's worth spending the time on it right now. Great suggestion though, we should cross-reference with the existing checkout form issue (#1061 and #1222). Merging!