Include topic info in JSON output parse of `bbs_database parse`

[FrancescoCasalegno]

Context

• We have implemented the commands bbs_database topic-extract to extract information about the topics of an article.
• However, this topic information is only used by bbs_database topic-extract to determine, based on user-defined inclusion/exclusion criteria, whether or not an article file should be parsed into a JSON (with bbs_database parse) and then uploaded into the database.
• We would like this information to be preserved also into the articles table, so that later on we can e.g. filter articles by topic.

Actions

• Include information on the topic in the JSON output parse of bbs_database parse.