Implement official discourse SSO on a fresh discourse install. This should lead to a much more stable discourse instance than the one we're currently using.

https://meta.discourse.org/t/official-single-sign-on-for-discourse/13045

Goals

Line demarcates "initial release", everything after the line is stretch goals

V2

• Login (basic SSO)
• Sync avatar

• Sync pro_expires_at
• Display PRO badge on forums
• Sync cover image
• Sync profile info (location, website, etc.)

V3

• Login (basic SSO)
• Sync avatar
• Sync pro_expires_at
• Sync cover image
• Sync profile info (location, website, etc.)
• Sync permissions with SSO moderator and admin
• Sync bans to forums

• Logout when main site logs out
• Sync ignoring/blocking w/ Discourse "muted users"
• Display Discourse notifications amongst main site notifications