feat: Support connecting to the API on localhost

This is a temporary solution, which adds an exception for 10.0.2.2,
allowing access over HTTP (without TLS). Once the app is
production-ready, it should use a publically hosted API.

app/src/main/AndroidManifest.xml

@@ -5,6 +5,7 @@
     <uses-permission android:name="android.permission.INTERNET" />
 
     <application
+        android:networkSecurityConfig="@xml/network_security_config"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"

app/src/main/java/com/p_vacho/neat_calendar/api/RetrofitClient.kt

@@ -10,7 +10,8 @@ import android.util.Log
 import okhttp3.ResponseBody
 
 object RetrofitClient {
-    private const val BASE_URL = "https://90f2-213-160-184-230.ngrok-free.app"
+    // Points to localhost on the machine running the emulator
+    private const val BASE_URL = "http://10.0.2.2:8000"
 
     private val retrofit: Retrofit by lazy {
         Retrofit.Builder()

app/src/main/res/xml/network_security_config.xml

@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
-  
-</PreferenceScreen>
+<network-security-config xmlns:android="http://schemas.android.com/apk/res/android">
+    <domain-config cleartextTrafficPermitted="true">
+        <domain includeSubdomains="true">10.0.2.2</domain>
+    </domain-config>
+</network-security-config>