Moderation

### Why

Moderation is essential to community management. There are two type of moderation:

* Membership: who can join, who can't join(block)
* Content moderation: which message should be shared

### Membership

Currently, a hub can only be public to everyone or private to a specific gateway.Also, only 1 3rd-party auth is implemented(google OAuth). Other extensions can be added when needed.

### Content moderation

It's still an open problem about moderating contents on a decentralized system. One way to solve it is to allow users share their **view** on the global state. Every user can have their opinion on what should/shouldn't be on the aggregated global state. Everyone can choose which view he/she want to follow.

However, this method inherently creates a power hierarchy on users. The more popular a user's view is, more power the user has.

Essentially, moderation is about delegation. It requires a balance between power and freedom. We need to explore more about the problem and potential solutions.