fix: Fix boundaries for full period payed in advance

[vincent-pochet]

Context

With the new multiple plans feature, the issuing date of the invoice have been updated to be the previous day of the invoice generation.

Description

Before the change, in the case of a plan payed in advance, the issuing date was the invoice creation date and so the first day of the new invoice period.

The issuing date field was used to recompute bounds of the invoice in the case of a trial period.

Before:

issuing_date = DateTime.parse('2022-03-01')
invoiced_from_date = issuing_date // 2022-03-01
invoiced_to_date = issuing_date.end_of_month // 2022-03-31

After:

issuing_date = DateTime.parse('2022-28-02')
invoiced_from_date = issuing_date // 2022-02-28
invoiced_to_date = issuing_date.end_of_month // 2022-02-28

Also, the code was not taking the plan interval into account, it was only working with monthly interval... 🐞

Note: the bounds computation will be delegated to a proper date service with the coming anniversary date feature

How Has This Been Tested?

QA have been performed locally

[jdenquin]

🐞 🔫