Minor cleanup form ui

Load form on trigger

Added Additional translations

Minor rename form and boolean flag

Fixed field labels and descriptions

Scaffold form tests

Basic tests for default states

Added test data from new endpoint

Filter start events from events array

Added tests for dropdown behaviour

Start events will have can_be_start_event=true,
stop events can only be set after a start event,
the stop events displayed depends on the start
event selected.

Added test for custom_stage_form submission

Minor refactor test helpers