In the API, enable to filter the packages of a project by PURL

[AnotherDaniel]

When using the REST API, it would be useful to be able to filter project packages by PURL, like this:

http://localhost:8001/api/projects/<uuid>/packages/?purl=pkg:cargo/json@0.12.4

[tdruez]

@AnotherDaniel thanks for the suggestion, added in #1450

[AnotherDaniel]

Wow that was fast, thanks!