Add filtering by item categories to donations and purchases

[cielf]

Summary

Add filtering by item categories to donations and purchases

Why?

Getting the totals donated or purchased for an item category is useful for grant-writing and reporting purposes.

Details

This should work similarly to the distribution, including making both the number of items and the value of the items correspond to only the items in the category chosen (there is an issue in flight around that for the distributions)

NOTE: The filtering affects both the index and the exports

Criteria for completion

• behaviour as described above
• tests to support that behaviour
• may need to have the user guide updated

[Naraveni]

can I take this

[cielf]

We usually just assign one at a time , but please check back when you've submitted the PR for the first one!

[Naraveni]

hey, I can take this one now, I complete my previous issue

[cielf]

Go ahead. then.