When Chwala's client requests document editing session Chwala should create access_token that will be passed by WOPI clients to KolabWopi, which then will communicate with Chwala using this token as Chwala session token.
access_token:
Important part is that this is not Chwala session key. This have to be a separate token, but Chwala need to accept it as an authentication token.
file_id:
This is the document session id which we use now with Manticore and Chwala's document API.