### What needs to get done Allow us to use grammar for at least the url field of `package-repositories`. ### Why it needs to get done If I want to enable `deb-src` and build a rock for both amd64 and arm64, I need something like this: ``` package-repositories: - type: apt formats: [deb, deb-src] components: - main - restricted - universe - multiverse suites: - questing url: http://archive.ubuntu.com/ubuntu key-id: F6ECB3762474EDA9D21B7022871920D1991BC93C - type: apt formats: [deb, deb-src] components: - main - restricted - universe - multiverse suites: - questing url: http://ports.ubuntu.com/ key-id: F6ECB3762474EDA9D21B7022871920D1991BC93C ``` But this then causes issues with apt because the architecture isn't available. It would be nice to be able to say: ``` package-repositories: - type: apt formats: [deb, deb-src] components: - main - restricted - universe - multiverse suites: - questing url: - to amd64: http://archive.ubuntu.com/ubuntu - else: http://ports.ubuntu.com key-id: F6ECB3762474EDA9D21B7022871920D1991BC93C ```