Add GPT4 models

Author: OkGoDoIt

OpenAI_API/Model/Model.cs

@@ -143,6 +143,16 @@ public Model()
 		/// </summary>
 		public static Model ChatGPTTurbo0301 => new Model("gpt-3.5-turbo-0301") { OwnedBy = "openai" };
 
+		/// <summary>
+		/// More capable than any GPT-3.5 model, able to do more complex tasks, and optimized for chat. Will be updated with the latest model iteration.  Currently in limited beta so your OpenAI account needs to be whitelisted to use this.
+		/// </summary>
+		public static Model GPT4 => new Model("gpt-4") { OwnedBy = "openai" };
+
+		/// <summary>
+		/// Same capabilities as the base gpt-4 mode but with 4x the context length. Will be updated with the latest model iteration.  Currently in limited beta so your OpenAI account needs to be whitelisted to use this.
+		/// </summary>
+		public static Model GPT4_32k_Context => new Model("gpt-4-32k") { OwnedBy = "openai" };
+
 		/// <summary>
 		/// Stable text moderation model that may provide lower accuracy compared to TextModerationLatest.
 		/// OpenAI states they will provide advanced notice before updating this model.

OpenAI_Tests/ChatEndpointTests.cs

@@ -84,12 +84,14 @@ public void SimpleCompletion()
 			Assert.IsNotEmpty(results.ToString());
 		}
 
-		[Test]
-		public void ChatBackAndForth()
+		[TestCase("gpt-3.5-turbo")]
+		[TestCase("gpt-4")]
+		public void ChatBackAndForth(string model)
 		{
 			var api = new OpenAI_API.OpenAIAPI();
 
 			var chat = api.Chat.CreateConversation();
+			chat.Model = model;
 
 			chat.AppendSystemMessage("You are a teacher who helps children understand if things are animals or not.  If the user tells you an animal, you say \"yes\".  If the user tells you something that is not an animal, you say \"no\".  You only ever respond with \"yes\" or \"no\".  You do not say anything else.");
 			chat.AppendUserInput("Is this an animal? Cat");