Renamed PlaceholderFragment -> SplashFragment

app/src/main/java/io/xxlabs/messenger/main/ui/PlaceholderFragment.kt

-package io.xxlabs.messenger.main.ui
-
-class MainFragment {
-}
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app/src/main/java/io/xxlabs/messenger/main/ui/SplashScreenFragment.kt

+package io.xxlabs.messenger.main.ui
+
+import androidx.fragment.app.Fragment
+
+/**
+ * Placeholder screen during app initialization.
+ */
+class SplashScreenFragment : Fragment() {
+}
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app/src/main/res/layout/fragment_splash_screen.xml

+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="@drawable/bg_splash_screen" />
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app/src/main/res/navigation/nav_graph.xml

 <?xml version="1.0" encoding="utf-8"?>
 <navigation xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/nav_graph"
-    app:startDestination="@id/coldStartActivity">
+    app:startDestination="@id/splashScreenFragment">
 
     <include app:graph="@navigation/nav_home" />
     <include app:graph="@navigation/nav_registration" />
 
-    <activity
-        android:id="@+id/coldStartActivity"
-        android:name="io.xxlabs.messenger.main.ui.MainActivity"
-        android:label="ColdStartActivity" />
+    <fragment
+        android:id="@+id/splashScreenFragment"
+        android:name="io.xxlabs.messenger.main.ui.SplashScreenFragment"
+        android:label="SplashScreenFragment"
+        tools:layout="@layout/fragment_splash_screen" />
 </navigation>
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