Update AuthenticationActivity (which extends BaseActivity class instead of Acitivity class)

app/src/main/java/chat/rocket/android/app/AuthenticationActivity.kt

 package chat.rocket.android.app
 
-import android.app.Activity
-import android.app.Fragment
 import android.os.Bundle
+import chat.rocket.android.BaseActivity
 import chat.rocket.android.R
 
 /**
  * @author Filipe de Lima Brito (filipedelimabrito@gmail.com)
  */
-class AuthenticationActivity : Activity() {
+class AuthenticationActivity : BaseActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_authentication)
 
         LayoutHelper.androidBug5497Workaround(this)
-        addFragment(AuthenticationLoginFragment(), "authenticationServerFragment")
-    }
-
-    private fun addFragment(fragment: Fragment, tag: String) {
-        fragmentManager.beginTransaction().add(R.id.fragment_container, fragment, tag).commit()
+        addFragment(AuthenticationLoginFragment(), "authenticationServerFragment", R.id.fragment_container)
     }
 }
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