Finish basic work on event participants

[mrkvon]

@regenerativecommunity

• Export pdf with attendance-list (Talita)

• Delete application correctly (Talita)

• Handling errors while adding a participant ()

• Mobile view (Talita)

• Create new user as participant (Michal) Implement adding a participant that isn't in database #127

• Update participant (Michal) Implement updating participant's data #129

• Delete participant (Michal) Implement removing participant #128

• Follow-up of Implement adding a participant that isn't in database #127, Implement removing participant #128, Implement updating participant's data #129 - make better UX for it (show that something is happening when saving data, keep editing when api fails)

• (maybe) Import participants from xls

• (maybe) bulk actions - applications - Delete many applications, add many participants at once.