- fix bug where `pageNumber` and `pageSize` were swapped during default
initialization in `apps.go`.
- fix bug in `pagingRequest.go` where `ToParams` mapped keys to the
incorrect struct fields.
- add `ForPageNumber` and `WithPageSize` functional options to allow
custom paging configuration.
- enhance `Apps` endpoint tests to verify that `pageNumber` and
`pageSize` query parameters are correctly passed to the API.
- add test case for verifying non-default paging options.