Create an instruction for how un-/rebooking of SJ tickets work and how the
Ombokningsvärde/Värdebevis are then used.
See pre-existing notes in
Ombokningsvärde/Värdebevis
https://docs.google.com/spreadsheets/d/17IPPyr-zsHv0ZCB_8YBISUqgwv3NGn02h2x3x8MAzDo/edit#gid=0