All endpoints are plural

Pagination information (next, prev, first, last) is included in the Link
HTTP header.
The total number of entries is provided in the X-Total-Count HTTP
header.

text is really generic and could conflict with another variable.
body is often used for comments.

+ fix tests

This allows to easily register items via the API without giving an ICS
id.

Split API in different blueprints like for the web UI:
- users (login)
- inventory
- network

Use version in API url (api/v1) to make future changes easier without
breaking backward compatibility