Custom package collections

[finestructure]

Custom package collections are a way to create a collection of packages that is searchable on SPI and adds a badge to the package page of participating packages.

The canonical example are SSWG incubated packages, which would be grouped by the incubation stage and show the appropriate badge on the package page, e.g. "SSWG Graduated".

I presented our design to the SSWG recently and it was accepted.

https://www.icloud.com/freeform/06f2y-34zSpXMHgo0heqXBPtQ#Custom_package_collections

Implementing this is part of our contribution to the SSWG's 2024 goals.