Add Forum retriever background job processing

[amindadgar]

We need to add the forum retriever to the background job processing as we need to answer a huge number of user requests. We could either go with redis or Celery but additional research must be done in case of background job monitoring.

[amindadgar]

This issue will be resolved using the hivemind-bot repo using the Celery app as it supports concurrent job processing. https://github.com/TogetherCrew/hivemind-bot

Another issue is already defined for this in hivemind-bot repo TogetherCrew/hivemind-bot#2