chore: added App IEndpoint type

src/Twilio/Types/App.cs

@@ -0,0 +1,42 @@
+using System;
+
+namespace Twilio.Types
+{
+    /// <summary>
+    /// App Endpoint
+    /// </summary>
+    public class App : IEndpoint
+    {
+        public const string PREFIX = "app:";
+
+        private readonly string _app;
+
+        /// <summary>
+        /// Create new app
+        /// </summary>
+        /// <param name="app">App name</param>
+        public App(string app)
+        {
+            if (string.IsNullOrEmpty(app))
+            {
+                throw new ArgumentException("Parameter 'app' cannot be null or empty.", nameof(app));
+            }
+
+            if (!app.ToLower().StartsWith(PREFIX))
+            {
+                app = PREFIX + app;
+            }
+
+            _app = app;
+        }
+
+        /// <summary>
+        /// Convert to string
+        /// </summary>
+        /// <returns>String representation</returns>
+        public override string ToString()
+        {
+            return _app;
+        }
+    }
+}

test/Twilio.Test/Types/AppTest.cs

@@ -0,0 +1,23 @@
+using System;
+using NUnit.Framework;
+using Twilio.Exceptions;
+using Twilio.Types;
+
+namespace Twilio.Tests.Types
+{
+    [TestFixture]
+    public class AppTest
+    {
+        [Test]
+        public void TestToString()
+        {
+            Assert.AreEqual("app:me", new App("me").ToString());
+            Assert.AreEqual("app:YOU", new App("YOU").ToString());
+            Assert.AreEqual("APP:HIM", new App("APP:HIM").ToString());
+            Assert.AreEqual("aPp:her", new App("aPp:her").ToString());
+            Assert.Throws<ArgumentException>(() => new App("").ToString());
+            Assert.AreEqual("app:AP12345?mycustomparam1=foo&mycustomparam2=bar", new App("app:AP12345?mycustomparam1=foo&mycustomparam2=bar").ToString());
+            Assert.AreEqual("app:AP12345?mycustomparam1=foo&mycustomparam2=bar", new App("AP12345?mycustomparam1=foo&mycustomparam2=bar").ToString());
+        }
+    }
+}