Prior to this commit, only system users had this pass.
Another significant change of the PR, is to make membership of a channel the angular stone of the permission check to create/update/stop streaming a message. The idea being, if you are a member of a channel already we don't need to check if you can join it AGAIN.
We also have `Chat::AutoRemove::HandleCategoryUpdated` which will deal with permissions change so it's simpler and less prone to error to consider the membership as the only source of truth.
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