feat(session): track user notification settings

Same pattern as language/preferences — Notifications settings page reads
current subscribed state from here.

Outpost/Root/SessionStore.swift

@@ -17,6 +17,7 @@ final class SessionStore {
     var userAvatarURL: URL?
     var userLanguage: String?
     var userPreferences: OutlineUserPreferences?
+    var userNotificationSettings: [String: Bool]?
     var teamName: String?
     var teamAvatarURL: URL?
     private(set) var apiClient: OutlineAPIClient?
@@ -77,6 +78,7 @@ final class SessionStore {
         userAvatarURL = nil
         userLanguage = nil
         userPreferences = nil
+        userNotificationSettings = nil
         teamName = nil
         teamAvatarURL = nil
         apiClient = nil
@@ -101,6 +103,7 @@ final class SessionStore {
         userAvatarURL = user.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
         userLanguage = user.language
         userPreferences = user.preferences
+        userNotificationSettings = user.notificationSettings
     }
 
     private func apply(user: OutlineUser, team: OutlineTeam, serverURL: URL) {
@@ -113,6 +116,7 @@ final class SessionStore {
         userAvatarURL = user.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
         userLanguage = user.language
         userPreferences = user.preferences
+        userNotificationSettings = user.notificationSettings
         teamName = team.name
         teamAvatarURL = team.avatarUrl.flatMap { URL(string: $0, relativeTo: serverURL)?.absoluteURL }
     }