feat: adds Default to CompletionUsage (#387)

Author: paulhendricks

async-openai/src/types/chat.rs

@@ -85,7 +85,7 @@ pub struct FunctionCall {
 }
 
 /// Usage statistics for the completion request.
-#[derive(Debug, Deserialize, Serialize, Clone, PartialEq)]
+#[derive(Debug, Deserialize, Serialize, Clone, PartialEq, Default)]
 pub struct CompletionUsage {
     /// Number of tokens in the prompt.
     pub prompt_tokens: u32,
@@ -100,7 +100,7 @@ pub struct CompletionUsage {
 }
 
 /// Breakdown of tokens used in a completion.
-#[derive(Debug, Deserialize, Serialize, Clone, PartialEq)]
+#[derive(Debug, Deserialize, Serialize, Clone, PartialEq, Default)]
 pub struct PromptTokensDetails {
     /// Audio input tokens present in the prompt.
     pub audio_tokens: Option<u32>,
@@ -109,7 +109,7 @@ pub struct PromptTokensDetails {
 }
 
 /// Breakdown of tokens used in a completion.
-#[derive(Debug, Deserialize, Serialize, Clone, PartialEq)]
+#[derive(Debug, Deserialize, Serialize, Clone, PartialEq, Default)]
 pub struct CompletionTokensDetails {
     pub accepted_prediction_tokens: Option<u32>,
     /// Audio input tokens generated by the model.