Drop three User fields we aren't keeping up to date; verify that's all

lib/api/model/model.dart

@@ -188,18 +188,25 @@ enum Emojiset {
 /// in <https://zulip.com/api/register-queue>.
 @JsonSerializable(fieldRename: FieldRename.snake)
 class User {
+  // When adding a field to this class:
+  //  * If a [RealmUserUpdateEvent] can update it, be sure to add
+  //    that case to [RealmUserUpdateEvent] and its handler.
+  //  * If the field can never change for a given Zulip user, mark it final.
+  //  * (If it can change but [RealmUserUpdateEvent] doesn't cover that,
+  //    then that's a bug in the API; raise it in `#api design`.)
+
   final int userId;
   String? deliveryEmail;
   String email;
   String fullName;
-  String dateJoined;
+  final String dateJoined;
   bool isActive; // Really sometimes absent in /register, but we normalize that away; see [InitialSnapshot.realmUsers].
-  bool isOwner;
-  bool isAdmin;
-  bool isGuest;
+  // bool isOwner; // obsoleted by [role]; ignore
+  // bool isAdmin; // obsoleted by [role]; ignore
+  // bool isGuest; // obsoleted by [role]; ignore
   bool? isBillingAdmin; // TODO(server-5)
-  bool isBot;
-  int? botType; // TODO enum
+  final bool isBot;
+  final int? botType; // TODO enum
   int? botOwnerId;
   @JsonKey(unknownEnumValue: UserRole.unknown)
   UserRole role;
@@ -214,7 +221,7 @@ class User {
   Map<int, ProfileFieldUserData>? profileData;
 
   @JsonKey(readValue: _readIsSystemBot)
-  bool isSystemBot;
+  final bool isSystemBot;
 
   static Map<String, dynamic>? _readProfileData(Map<dynamic, dynamic> json, String key) {
     final value = (json[key] as Map<String, dynamic>?);
@@ -240,9 +247,6 @@ class User {
     required this.fullName,
     required this.dateJoined,
     required this.isActive,
-    required this.isOwner,
-    required this.isAdmin,
-    required this.isGuest,
     required this.isBillingAdmin,
     required this.isBot,
     required this.botType,

test/api/model/model_checks.dart

@@ -8,9 +8,6 @@ extension UserChecks on Subject<User> {
   Subject<String> get fullName => has((x) => x.fullName, 'fullName');
   Subject<String> get dateJoined => has((x) => x.dateJoined, 'dateJoined');
   Subject<bool> get isActive => has((x) => x.isActive, 'isActive');
-  Subject<bool> get isOwner => has((x) => x.isOwner, 'isOwner');
-  Subject<bool> get isAdmin => has((x) => x.isAdmin, 'isAdmin');
-  Subject<bool> get isGuest => has((x) => x.isGuest, 'isGuest');
   Subject<bool?> get isBillingAdmin => has((x) => x.isBillingAdmin, 'isBillingAdmin');
   Subject<bool> get isBot => has((x) => x.isBot, 'isBot');
   Subject<int?> get botType => has((x) => x.botType, 'botType');

test/example_data.dart

@@ -94,9 +94,6 @@ User user({
     fullName: fullName ?? 'A user', // TODO generate example names
     dateJoined: '2023-04-28',
     isActive: isActive ?? true,
-    isOwner: false,
-    isAdmin: false,
-    isGuest: false,
     isBillingAdmin: false,
     isBot: isBot ?? false,
     botType: null,