Start working on Matrix config

hosts/cube/matrix.nix

@@ -0,0 +1,30 @@
+{ config, ulib, ... }: with ulib;
+
+# Documenting this because I found the way Matrix works a bit weird:
+#
+# Since it uses normal plain HTTP on ports 80 and 443, we are using
+# the root domain and proxying ${domain}/_matrix to the local matrix
+# instance that is running. This means there are no matrix or chat
+# or whatever 3rd level domains in this setup. The server url is
+# the root, everywhere.
+
+let
+  inherit (config.networking) domain;
+in serverSystemConfiguration {
+  age.secrets."cube/password.matrix".owner      = "matrix";
+  age.secrets."cube/password.matrix.sync".owner = "matrix";
+
+  services.postgresql = {
+    ensureDatabases = [ "matrix" ];
+    ensureUsers     = [{
+      name = "matrix";
+      ensureDBOwnership = true;
+    }];
+  };
+
+  services.matrix-synapse = { # enabled {
+    settings = {
+      server_name = domain;
+    };
+  };
+}