feat: add monthly quota periods

[lukasdotcom]

This does the minimum to fix this adding a monthly option for period that resets every month or exact multiple of months. This could also be used for yearly as long as a start date of January is ok. The date range was originally planned to be put into the admin settings, but I think it looks better in personal settings.
Resolves part of: #250

Admin Settings

Personal Settings

[julien-nc]

When there is no value for quota_period, one loads the admin settings page, switches Reset quota every from 30 days to 30 months, then it fails to save because it tries to save without the "day" param. It should be one by default if it's not set, just like it is visually 1 by default.

Could you also add a bit more descriptions of what the methods do?

[lukasdotcom]

When there is no value for quota_period, one loads the admin settings page, switches Reset quota every from 30 days to 30 months, then it fails to save because it tries to save without the "day" param. It should be one by default if it's not set, just like it is visually 1 by default.

Could you also add a bit more descriptions of what the methods do?

I remember that issue, but forgot about it when I manually fixed the config. Thanks for noticing it. Is fixed and rebased now.