Moves creation of notification channel to app startup (#32)

Co-authored-by: Jakob Möller <jakob.moeller@sap.com>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/CoronaWarnApplication.kt

@@ -2,6 +2,7 @@ package de.rki.coronawarnapp
 
 import android.app.Application
 import android.content.Context
+import de.rki.coronawarnapp.notification.NotificationHelper
 
 class CoronaWarnApplication : Application() {
 
@@ -13,6 +14,7 @@ class CoronaWarnApplication : Application() {
 
     override fun onCreate() {
         instance = this
+        NotificationHelper.createNotificationChannel()
         super.onCreate()
     }
 }

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/notification/NotificationHelper.kt

@@ -128,7 +128,6 @@ object NotificationHelper {
      * @param visibility: Int
      */
     fun sendNotification(title: String, content: String, visibility: Int) {
-        createNotificationChannel()
         val notification = buildNotification(title, content, visibility) ?: return
         with(NotificationManagerCompat.from(CoronaWarnApplication.getAppContext())) {
             notify(Random.nextInt(), notification)

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/main/MainFragment.kt

@@ -150,7 +150,6 @@ class MainFragment : BaseFragment() {
                         NotificationManagerCompat.from(requireContext()).areNotificationsEnabled()
                             .toString()
                     )
-                    NotificationHelper.createNotificationChannel()
                     NotificationHelper.sendNotification(
                         getString(R.string.notification_headline),
                         getString(R.string.notification_body),