Extend GET /iicense and /obligation endpoints

[deo002]

Description

Extend GET /license and GET /obligation endpoints with a query paramenter search_term to fetch results which match with the search term.

• For the /license endpoint, the entries which have the search term either in full name, short name, text or spdx expression need to be returned.
• For the /obligation endpoint, the entries with the search term either in topic or text need to be returned.