Reverse forening type priority
Convert pub_date to date of import if missing
Move conversion to logical placement
Prefetch related dates on aktivitet lookup
Reorder conversion methods
Add date relation conversion logic
Let date convert method handle new object creation
No need to return the object after conversion
Convert start- and end-date
Convert signup deadline
Fix semicolons
Allow unlimited participant count
Convert signup max allowed
Convert date_cancel field to correct new model field

date_cancel field corresponds to signup_cancel_deadline, not signup_deadline
Convert signup date start/deadline