As a user, I can request paginated search results from the API

[bterone]

Why

Currently, the search_result index in the API returns all the search results associated with the user. We need to add pagination so that we can query a selection of data, and will have more space to introduce the "relationship" and "included" attributes as part of the JSONAPI spec.

Acceptance Criteria

1/ Introduce pagination to the API
2/ Add the "relationship" and "included" attribute to the search result index.