Add searching option to listing user profiles endpoint

[mario-nt]

The API endpoint for getting the list of user profiles can be improved by accepting the search query param to allow users to search for a specific torrent or torrents.

Example: http://localhost:3001/users?search=john+doe&pageSize=50&page=1

Part of torrust/torrust-index-gui#659 and torrust/torrust-index#799