add diffing for a lot of events

lib/helpers/extensions/displayname_color.dart

@@ -20,6 +20,15 @@ extension DisplaynameColor on WidgetRef {
     ),
   };
 
+  /// Like [displaynameColor], for when [userId]'s [level] is already known,
+  /// like a level they're being given.
+  Color displaynameColorAt(String userId, double level) => switch (watch(
+    SettingsController.provider.select((settings) => settings.value?.nameColor),
+  )) {
+    .user => userId.colorHash,
+    .powerLevel || null => powerLevelColor(level),
+  };
+
   static Color powerLevelColor(double level) => HSLColor.fromAHSL(
     1,
     level.isInfinite ? 30 : (210 + level / 50 * 137.50776) % 360,

lib/helpers/extensions/join_rule_name.dart

@@ -0,0 +1,13 @@
+import "package:nexus/models/join_rule.dart";
+
+extension JoinRuleName on JoinRule {
+  /// What the rule is called in the UI, e.g. "Invite only".
+  String get displayName => switch (this) {
+    .public => "Public",
+    .invite => "Invite only",
+    .knock => "Knock",
+    .restricted => "Restricted",
+    .knockRestricted => "Restricted or knock",
+    .private => "Private",
+  };
+}