ResearchContextAPI: implement extend_research_context feature

[alebg]

Implement a new feature to extend research contexts. The idea is that we'll get an existing research context, and based on it, we'll create a new one that has the same source data, plus some additional. As inputs, we would need:

• research context title
• research context description
• pre-existing research context ID
• source data ID list

Error cases:

• The pre-existing research context doesn't exist
• No new source data is actually passed. I.e., the source data ID list is already contained in the source data ID list of the pre-existing research context

Two relevant features to look at are new_research_context and list_source_data_for_research_context. Most likely, all secondary side functionalities are already present. So we just need:

• A usecase
• A presenter
• A controller
• An endpoint