Ability to blacklist users from contacting you. (SPEC-123)

[matrixbot]

We currently have no way of asking you server to blacklist groups of users from ever trying to contact you. This is a pretty important abuse avoidance metric.

Open questions include:

• Per-user or per-group (need a generic way to manage lists of users then, but we kinda need that anyway)
• Ignore invites, or all traffic from these users?
• Can we build this into reputation analysis?

The use case here is that someone invites you to a chat, either with a nasty name or nasty contents after you accept the invite, and you never want to see them again.

(Imported from https://matrix.org/jira/browse/SPEC-123)

(Reported by @ara4n)

[matrixbot]

Jira watchers: @ara4n

[matrixbot]

Links exported from Jira:

relates to #528

[ara4n]

i /think/ this is covered by https://docs.google.com/document/d/1Jex7lDAwmv0KcgyL9oeGfUCsjw0CWSqedPKZ1ViSVis/edit (albeit conflated with #528)

[richvdh]

I'm failing to grok how this was different from #528, so closing it now in the hope that if we've missed something, somebody will open a new issue clarifying what is still missing.