Limit and adjust default pagination params

[samuel-rufi]

Description

Currently, we don't have a limit for the page_size param in place.
Furthermore, it shouldn't be possible to pass 0 as pagination param as of a wrong offset calculation.

The default value “page_size” should be set to “50” instead of “10”, as “10” seems to be too few results. As we also use “50” in other queries, we should set the default value to this value.