Completion API: add new params (#870)

* Completion API: add 'store' param

This param allows you to opt a completion request in to being stored,
for use in distillations and evals.

* Add cached and audio tokens to usage structs

These have been added to the completions API recently:
https://platform.openai.com/docs/api-reference/chat/object#chat/object-usage

common.go

@@ -7,10 +7,18 @@ type Usage struct {
 	PromptTokens            int                      `json:"prompt_tokens"`
 	CompletionTokens        int                      `json:"completion_tokens"`
 	TotalTokens             int                      `json:"total_tokens"`
+	PromptTokensDetails     *PromptTokensDetails     `json:"prompt_tokens_details"`
 	CompletionTokensDetails *CompletionTokensDetails `json:"completion_tokens_details"`
 }
 
 // CompletionTokensDetails Breakdown of tokens used in a completion.
 type CompletionTokensDetails struct {
+	AudioTokens     int `json:"audio_tokens"`
 	ReasoningTokens int `json:"reasoning_tokens"`
 }
+
+// PromptTokensDetails Breakdown of tokens used in the prompt.
+type PromptTokensDetails struct {
+	AudioTokens  int `json:"audio_tokens"`
+	CachedTokens int `json:"cached_tokens"`
+}

completion.go

@@ -239,6 +239,9 @@ type CompletionRequest struct {
 	// incorrect: `"logit_bias":{"You": 6}`, correct: `"logit_bias":{"1639": 6}`
 	// refs: https://platform.openai.com/docs/api-reference/completions/create#completions/create-logit_bias
 	LogitBias map[string]int `json:"logit_bias,omitempty"`
+	// Store can be set to true to store the output of this completion request for use in distillations and evals.
+	// https://platform.openai.com/docs/api-reference/chat/create#chat-create-store
+	Store           bool     `json:"store,omitempty"`
 	LogProbs        int      `json:"logprobs,omitempty"`
 	MaxTokens       int      `json:"max_tokens,omitempty"`
 	N               int      `json:"n,omitempty"`