New date helper functions

[bpuig]

Change getTotalDurationInDays, getDaysUntilEnds, getDaysUntilTrialEnds, getRemainingPeriodProportion for more flexible methods.

Breaking changes

getDaysUntilTrialEnds is now getTrialPeriodRemainingUsageIn('day') getTotalDurationInDays is now getSubscriptionTotalDurationIn('day') getDaysUntilEnds is now getSubscriptionPeriodRemainingUsageIn('day') getRemainingPeriodProportion is now getRemainingSubscriptionPeriodProportion() getRemainingPriceProrate is now getSubscriptionRemainingUsagePriceProrate()

TODO

• [x] Helper to calculate periods and diffs
• [x] Trial period functions
• [x] Subscription period functions
• [x] Duplicate trial data on subscription
  • [x] Create own trait for getTrialTotalDurationIn

[bpuig]

This gives flexibility to period calculation and comparison and also solves @boryn question https://github.com/bpuig/laravel-subby/pull/77#issuecomment-862897110 about copying trial values into subscription