Consult rule / example based agents (Dialogflow) before looking up text in database

[MrOrz]

As-is

Currently for some common interactions like "Hello", "Hi", or "Thanks", we need to create an article and reply to teach users to use Cofacts lookup feature correctly.

To-be

We can integrate rule / example based agents for such interaction. More specifically,

• We can build rule-based agents using Dialogflow, specifying examples and sample responses there.
• When we detect new messages here (or in initState handler), we first consult rule-based agents
  • If the agent returns fallback, proceed to ListArticles rumors-api call as before
  • If the agent returns a preset response, use the response directly.