Initialize navigation with AuthenticationFragment

Also remove unused MainFragment-related code

app/src/main/java/gq/kirmanak/mealie/MainActivity.kt

@@ -1,18 +1,13 @@
 package gq.kirmanak.mealie
 
-import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
-import gq.kirmanak.mealie.ui.main.MainFragment
+import androidx.appcompat.app.AppCompatActivity
+import gq.kirmanak.mealie.databinding.MainActivityBinding
 
 class MainActivity : AppCompatActivity() {
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        setContentView(R.layout.main_activity)
-        if (savedInstanceState == null) {
-            supportFragmentManager.beginTransaction()
-                .replace(R.id.container, MainFragment.newInstance())
-                .commitNow()
-        }
+        val binding = MainActivityBinding.inflate(layoutInflater)
+        setContentView(binding.root)
     }
 }

app/src/main/java/gq/kirmanak/mealie/ui/auth/AuthenticationFragment.kt

@@ -0,0 +1,28 @@
+package gq.kirmanak.mealie.ui.auth
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import gq.kirmanak.mealie.databinding.FragmentAuthenticationBinding
+
+class AuthenticationFragment : Fragment() {
+    private var _binding: FragmentAuthenticationBinding? = null
+    private val binding: FragmentAuthenticationBinding
+        get() = checkNotNull(_binding) { "Binding requested when fragment is off screen" }
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        _binding = FragmentAuthenticationBinding.inflate(inflater, container, false)
+        return binding.root
+    }
+
+    override fun onDestroyView() {
+        super.onDestroyView()
+        _binding = null
+    }
+}

app/src/main/java/gq/kirmanak/mealie/ui/main/MainFragment.kt

@@ -1,32 +0,0 @@
-package gq.kirmanak.mealie.ui.main
-
-import androidx.lifecycle.ViewModelProvider
-import android.os.Bundle
-import androidx.fragment.app.Fragment
-import android.view.LayoutInflater
-import android.view.View
-import android.view.ViewGroup
-import gq.kirmanak.mealie.R
-
-class MainFragment : Fragment() {
-
-    companion object {
-        fun newInstance() = MainFragment()
-    }
-
-    private lateinit var viewModel: MainViewModel
-
-    override fun onCreateView(
-        inflater: LayoutInflater, container: ViewGroup?,
-        savedInstanceState: Bundle?
-    ): View {
-        return inflater.inflate(R.layout.main_fragment, container, false)
-    }
-
-    override fun onActivityCreated(savedInstanceState: Bundle?) {
-        super.onActivityCreated(savedInstanceState)
-        viewModel = ViewModelProvider(this).get(MainViewModel::class.java)
-        // TODO: Use the ViewModel
-    }
-
-}

app/src/main/java/gq/kirmanak/mealie/ui/main/MainViewModel.kt

@@ -1,7 +0,0 @@
-package gq.kirmanak.mealie.ui.main
-
-import androidx.lifecycle.ViewModel
-
-class MainViewModel : ViewModel() {
-    // TODO: Implement the ViewModel
-}