Add "paid in full" datestamp to order along with "created" and "updated"

Similar to this issue #1166540: add ability to get order checkout date

That issue, however, seems to have a longer history related to order review and is trying to address several things at once. It seems to have only recently become relevant to what I'm looking for, after somebody re-opened a closed/fixed issue and renamed it.

Rather than doing that I'm opening a fresh issue to discuss an important problem.

Ryan pretty much sums up the use case here: http://www.bywombats.com/blog/01-24-2012/updating-completed-order-timest...

TL;DR: There's a problem with the discrepancy between order "created" and "paid" timestamps. If a user starts an order, doesn't checkout, and then comes back weeks later to make a payment, the order is lost on the order review screen (/admin/commerce/orders) because it gets buried by orders that are more recently created.

Worse yet.. The Commerce Kickstart setup give you filters at the top for date, and doesn't have any text near those filters that explains that orders may have been created long before they were paid for. So an admin goes in and filters to see orders completed in the last week, and the order that was created weeks ago but paid for yesterday doesn't appear. This is really bad UI.

In the above-mentioned post on bywombats.com, Ryan alters the "created" date with a rule. I don't think that is a solid fix because it overwrites a date value that may be useful to admins. Maybe an admin wants to have both the created date and the "paid" date? Overwriting the created date solves the problem but does so by creating a new problem. The created date should only reference what it stands for, the created date. Changing it will certainly cause confusion if the admin wants to know data about order creation.

This could be fixed if a new field were added to orders. "Date paid in full" -- it would be a simple time stamp just like "Created" and "Updated" stamps, but it would represent the time at which the order was paid for.

A rule similar to the rule Ryan created could set the value.

Then, the default view at "/admin/commerce/orders" would have to be updated to have that filter use the "paid in full" date rather than the "created" date...

I'm marking this as "major" because I think it's a huge problem that in the default configuration, orders can be easily lost. This came up on a site of mine that now has thousands of orders. Some were lost because admins were not seeing them when they were filtering the order review screen to a specific date range. It totally disrupted their order fulfillment process, and now fixing the problem is going to be a bit of a nightmare because I have to retrofit a "paid in full" date on orders that were already "Paid in full" -- I can't go back and fire rules, so this is going to take some ugly query writing to target when each past order was paid....