Students open the bot and search topics by keyword

[ricCap]

Implement the bot capability that lets a student search topics using a single keyword.

HTD: the user opens the bot and writes a keyword; the user is than shown a list of topics whose abstract/description match the keyword (define the policy); the user can then open the preview and follow a link to the thorough description. At the end the user has viewed the list of topics matching a given keyword and has downloaded/viewed the complete description of the topic.

A good way may be to use Elasticsearch indexes on top of a MongoDB and use a keyword policy that takes only the most confident results (a double index on Abstract and Description; the result would be a weighted sum with _score_abstract = _score(abstract) * k and _score_description = _score(description) * h, with k > h)