CompletionTokensDetails can be nil (should be optional) (#20)

* Update ChatCompletionChunk.swift

* Update ChatCompletionChunk.swift

* Update ChatCompletion.swift

Author: AlexKlim

Sources/LLMChatOpenAI/ChatCompletion.swift

@@ -162,14 +162,14 @@ public struct ChatCompletion: Decodable, Sendable {
 
         public struct CompletionTokensDetails: Decodable, Sendable {
             /// When using Predicted Outputs, the number of tokens in the prediction that appeared in the completion.
-            public let acceptedPredictionTokens: Int
+            public let acceptedPredictionTokens: Int?
 
             /// When using Predicted Outputs, the number of tokens in the prediction that did not appear in the completion.
             /// However, like reasoning tokens, these tokens are still counted in the total completion tokens for purposes of billing, output, and context window limits.
-            public let rejectedPredictionTokens: Int
+            public let rejectedPredictionTokens: Int?
 
             /// Tokens generated by the model for reasoning.
-            public let reasoningTokens: Int
+            public let reasoningTokens: Int?
 
             private enum CodingKeys: String, CodingKey {
                 case acceptedPredictionTokens = "accepted_prediction_tokens"

Sources/LLMChatOpenAI/ChatCompletionChunk.swift

@@ -154,14 +154,14 @@ public struct ChatCompletionChunk: Decodable, Sendable {
 
         public struct CompletionTokensDetails: Decodable, Sendable {
             /// When using Predicted Outputs, the number of tokens in the prediction that appeared in the completion.
-            public let acceptedPredictionTokens: Int
+            public let acceptedPredictionTokens: Int?
 
             /// When using Predicted Outputs, the number of tokens in the prediction that did not appear in the completion.
             /// However, like reasoning tokens, these tokens are still counted in the total completion tokens for purposes of billing, output, and context window limits.
-            public let rejectedPredictionTokens: Int
+            public let rejectedPredictionTokens: Int?
 
             /// Tokens generated by the model for reasoning.
-            public let reasoningTokens: Int
+            public let reasoningTokens: Int?
 
             private enum CodingKeys: String, CodingKey {
                 case acceptedPredictionTokens = "accepted_prediction_tokens"