[Sprint/CleverChipmunk](bug): (HotFix) Filtered out users banned #381

Unable to test locally

Suggested channels wont work for me locally, so if deployed this needs testing in staging. Also tried to hit the endpoint with postman and had no luck, so resolved to looking at the table layout in ./cqlsh to work out what fields the entity object has.

Ideally this should be dealt with at a lower level in ElasticSearch. I did look at Suggestions/Repository to make changes at query level, but after chatting Marcelo rightly pointed out that that wouldn't be very scalable to do for every endpoint, and have decided it best to submit a front-end fix as a patch, and recommend the banned channels get removed from the index.