Fixing broken reports functionality

[Shirkit]

Hello, it's me again.

So I've noticed for a while that reports were broken in some edge cases on my store, so I did a quick fix back then to keep using.

Now, I'm porting proper changes to the base repo, so that everyone has everything properly working.

This should fix for a lot of different stores using registrations, since the previous code did not cover for closed registrations, older orders, busy stores with lots of orders, and wasn't optmized to fetch the minimum amount of data from the DB.

As it stands now, I think it's a direct improvement on all fronts on this functionality.

PS: Sorry for the 2 commits, it's actually only one, but I don't know how to remove the 'merge' one that I did to update my fork.

[Shirkit]

Also, this should fix #35

[allysonsouza]

Hi @Shirkit, thanks again for your collaboration! I'm reviewing your pull request, and noticed some small things, but in general is a great enhancement to the plugin! I'll list my observations below:

• In the Reports > Events page, variations dates are only displayed after there's one registrations to the event (I though since they have their ID's already displayed, maybe the date could be displayed also);
• The participant phone is not a default field, so it's column in reports should not be as well;
• Some hooks could be added to the code, making the addition of new columns easier;
• I guess you could have used WP_Query to get the data, instead of creating a custom SQL query, but I did not dig into it to much;

The first two points are thing I would consider before the merge, the other two are just some suggestions for improvements.

Thanks again for collaborate with Registrations!

[allysonsouza]

Since WooCommerce has evolved and will probably soon remove it's old reports area, we'll work to integrate our reports with new analysis section or to develop or own reports for registrations.