refactor(test): unify Booking.by_date specs with .by_amount
refactor(test): unify Booking.by_date specs with .by_amount

The .by_date and .by_amount scopes have a similar interface and
should have similar scenarios tested.

This patch unifies the specs for .by_amount and .by_date.

huerlisi/has_accounts,huerlisi/has_accounts,hauledev/has_account,hauledev/has_account,hauledev/has_account,huerlisi/has_accounts