feat: T-955 Add service to find billable subscriptions

[vincent-pochet]

Subscription's billing date cases

With Monthly Plans

With subscription date billing period

• Day number is less than or equal to the last day of the current month (ie: less than or equal to 28 in february, less than or equal to 30 in april...)
  • Bill on the subscription day number every month, ei: Subscription date is on 13/04, billing will run on the 13th on each month, the billable period is from the 13th to the 12th 11:59pm of the next month.
• Day number is after last day of the current month (ie: subscription date on 30th but current month is february with only 28 days, subscription date on 31th but current month is april with only 30 days)
  • bill on the last day of the current month

With beginning of period billing period

• Bill on the first day of each month

With Yearly Plans

With subscription date billing period

• Subscription day is on 29th of february in a leap year
  • Bill on the 29th of february
• Subscription day is on 29th of february not in a leap year
  • Bill on the 28th of february
• Subscription day is any other day (ie: subscription date on 16th)
  • Bill on the subscription anniversary

With beginning of period billing period

• Bill on the first day of each year

[height]

This pull request has been linked to 1 task:

• T-955 [API] Find billable subsrciption (unlink task)

💡Tip: Add "Close T-955" to the pull request title or description, to a commit message, or in a comment to mark this task as "Done" when the pull request is merged.

[jdenquin]

Nice one!