api: Add emailAddressVisibility to InitialSnapshot

Also add `emailAddressVisibility` to `PerAccountStore`.

This is for backward compatibility to the Zulip server versions prior to
Zulip 7.0 (FL 163) where there was realm-level `email_address_visibility`
policy for which a user can see other user's real email address. Search
for "email_address_visibility" in https://zulip.com/api/register-queue.

This will become handy in the next commit(s) where the user's real email
is shown in it's profile page.

Note: This field is removed in Zulip 7.0 (FL 163) and replaced with:
* https://zulip.com/api/update-settings#parameter-email_address_visibility
* https://zulip.com/api/update-realm-user-settings-defaults#parameter-email_address_visibility

Author: sm-sayedi

lib/api/model/initial_snapshot.dart

@@ -24,6 +24,15 @@ class InitialSnapshot {
 
   final List<CustomProfileField> customProfileFields;
 
+  /// The realm-level policy for which a user can see other user's real email address.
+  ///
+  /// Search for "email_address_visibility" in https://zulip.com/api/register-queue.
+  ///
+  /// **Note:** This field is removed in Zulip 7.0 (FL 163) and replaced with:
+  ///   * https://zulip.com/api/update-settings#parameter-email_address_visibility
+  ///   * https://zulip.com/api/update-realm-user-settings-defaults#parameter-email_address_visibility
+  final EmailAddressVisibility? emailAddressVisibility;
+
   // TODO(server-8): Remove the default values.
   @JsonKey(defaultValue: 15000)
   final int serverTypingStartedExpiryPeriodMilliseconds;
@@ -94,6 +103,7 @@ class InitialSnapshot {
     required this.zulipMergeBase,
     required this.alertWords,
     required this.customProfileFields,
+    required this.emailAddressVisibility,
     required this.serverTypingStartedExpiryPeriodMilliseconds,
     required this.serverTypingStoppedWaitPeriodMilliseconds,
     required this.serverTypingStartedWaitPeriodMilliseconds,
@@ -117,6 +127,14 @@ class InitialSnapshot {
   Map<String, dynamic> toJson() => _$InitialSnapshotToJson(this);
 }
 
+enum EmailAddressVisibility {
+  @JsonValue(1) everyone,
+  @JsonValue(2) members,
+  @JsonValue(3) admins,
+  @JsonValue(4) nobody,
+  @JsonValue(5) moderators,
+}
+
 /// An item in `realm_default_external_accounts`.
 ///
 /// For docs, search for "realm_default_external_accounts:"

lib/api/model/initial_snapshot.g.dart

@@ -236,6 +236,7 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
       realmDefaultExternalAccounts: initialSnapshot.realmDefaultExternalAccounts,
       realmEmoji: initialSnapshot.realmEmoji,
       customProfileFields: _sortCustomProfileFields(initialSnapshot.customProfileFields),
+      emailAddressVisibility: initialSnapshot.emailAddressVisibility,
       accountId: accountId,
       selfUserId: account.userId,
       userSettings: initialSnapshot.userSettings,
@@ -269,6 +270,7 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
     required this.realmDefaultExternalAccounts,
     required this.realmEmoji,
     required this.customProfileFields,
+    required this.emailAddressVisibility,
     required this.accountId,
     required this.selfUserId,
     required this.userSettings,
@@ -311,6 +313,8 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
   final Map<String, RealmDefaultExternalAccount> realmDefaultExternalAccounts;
   Map<String, RealmEmojiItem> realmEmoji;
   List<CustomProfileField> customProfileFields;
+  /// For docs, please see [InitialSnapshot.emailAddressVisibility].
+  final EmailAddressVisibility? emailAddressVisibility;
 
   ////////////////////////////////
   // Data attached to the self-account on the realm.

lib/model/store.dart

@@ -575,6 +575,7 @@ InitialSnapshot initialSnapshot({
   String? zulipMergeBase,
   List<String>? alertWords,
   List<CustomProfileField>? customProfileFields,
+  EmailAddressVisibility? emailAddressVisibility,
   int? serverTypingStartedExpiryPeriodMilliseconds,
   int? serverTypingStoppedWaitPeriodMilliseconds,
   int? serverTypingStartedWaitPeriodMilliseconds,
@@ -599,6 +600,7 @@ InitialSnapshot initialSnapshot({
     zulipMergeBase: zulipMergeBase ?? recentZulipVersion,
     alertWords: alertWords ?? ['klaxon'],
     customProfileFields: customProfileFields ?? [],
+    emailAddressVisibility: EmailAddressVisibility.everyone,
     serverTypingStartedExpiryPeriodMilliseconds:
       serverTypingStartedExpiryPeriodMilliseconds ?? 15000,
     serverTypingStoppedWaitPeriodMilliseconds: