Remove duplicate history from the database

[lpiwowar]

Description

With this PR we introduced sending of the message history to the model [1]. The issue is that we are storing the history into the Thread table inside the database even though the history is already stored in Step table. This ultimately means that we are storing the history twice.

Let's make it possible for the chatbot to pull the history from the Step table and remove the duplicate data from Thread table.

[1] #56