Change current Pagination scheme from Offsetbased -> keybased

[HenrikHL]

The current implementation uses offset based pagination (this was for simplicity) - change it to key based to be aligned with the Design Guide specs.

Investigate if last_page cursor, prev_page cursor should be removed. If these pages are too complex to compute we could consider removing them from the Design Guide.

Investigate the complexity of having pagination with multiple sorting columns defined.
EX: sort=name,age:desc
If it turns out that this is too complex consider updating the Design Guide to reflect this

• change to key based pagination
• investigate if last_page and prev_page is possible to compute
• investigate if multiple sort columns is compatible with key based pagination