Include Pagination across the Spec

[taleodor]

Currently pagination is only added to /products endpoint, needs to be added to other relevant endpoints returning lists of elements.

[nscuro]

As suggested by @ppkarwasz in Slack, we should also consider not using offset-based pagination. Both from a stability and a performance perspective, paging by modification date or similar would be a better choice.

[taleodor]

Pagination was generally implemented via #195 . However, I'm keeping this open based on @nscuro comment above whether we should tweak the way we paginate.