Add sliding sync proxy for matrix

Sliding sync is a future version of the matrix spec, but the proxy can be
deployed while still allowing us to use a non-proxied version. Sliding
sync allows much faster client load times, etc. as the client no longer
needs to sync everything

also: rip out commented/disabled coturn code
Change-Id: I9026ed7dcaec961f1bc54469f18f04b68f6e3918
Reviewed-on: https://git.clicks.codes/c/Clicks/NixFiles/+/82
Tested-by: Skyler Grey <minion@clicks.codes>
Reviewed-by: Maddie H <maddie@clicks.codes>
diff --git a/modules/common/nginx/clicks.codes/.well-known/matrix b/modules/common/nginx/clicks.codes/.well-known/matrix
index c7ba524..57b6176 100644
--- a/modules/common/nginx/clicks.codes/.well-known/matrix
+++ b/modules/common/nginx/clicks.codes/.well-known/matrix
@@ -3,5 +3,8 @@
   "m.homeserver": {
     "base_url": "https://matrix-backend.clicks.codes:443",
     "server_name": "clicks.codes"
+  },
+  "org.matrix.msc3575.proxy": {
+    "url": "https://matrix-sliding-sync.clicks.codes"
   }
 }