[REF] Paypal ipn - cleanup references to completion

[REF] Paypal ipn - cleanup references to completion

This extracts a function to check if the contribution is completed.

I also rationalised the validation - it was using a combo of recur and first to
validate but on thinking it through I realised all it was saying was
'if we are finalising a pending contribution the amount must match'

I think that's fine even for recur with a change in amount - that seems
to me to be something that happens down the track but we still expect
the very first one to come in with the value it originally
had - if that is NOT true then we probably should just remove the check