presence: fix updates when app returns to active state

Change-Id: I2db33cb2efbdafe9bdb4b212abb89520d2b2c7d4

Ring/Ring/AppDelegate.swift

@@ -269,6 +269,13 @@ class AppDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterD
 
     func applicationDidBecomeActive(_ application: UIApplication) {
         self.clearBadgeNumber()
+        guard let account = self.accountService.currentAccount else { return }
+        self.presenceService.subscribeBuddies(withAccount: account.id, withContacts: self.contactsService.contacts.value, subscribe: true)
+    }
+
+    func applicationWillResignActive(_ application: UIApplication) {
+        guard let account = self.accountService.currentAccount else { return }
+        self.presenceService.subscribeBuddies(withAccount: account.id, withContacts: self.contactsService.contacts.value, subscribe: false)
     }
 
     func prepareVideoAcceleration() {

Ring/Ring/Services/PresenceService.swift

@@ -57,6 +57,10 @@ class PresenceService {
     func subscribeBuddy(withAccountId accountId: String,
                         withUri uri: String,
                         withFlag flag: Bool) {
+        if flag && contactPresence[uri] != nil {
+            // already subscribed
+            return
+        }
         presenceAdapter.subscribeBuddy(withURI: uri, withAccountId: accountId, withFlag: flag)
         if !flag {
             contactPresence[uri] = nil