CompletionBatchingRequestSupport

[NullpointerW]

solve iusse #201 i think this feature is useful
i closed pr #210 because I think there are too many unnecessary changes, here is a more concise change to implement

c := openai.NewClient("your token")
	ctx := context.Background()

	
	// test CreateCompletion
	reqNor := CompletionRequest{
		Prompt:    []string{"Lorem ipsum", "Lorem ipsum", "Lorem ipsum"}, //use string or []string 
		Model:     GPT3Curie,
		MaxTokens: 5,
	}
	resp, err := c.CreateCompletion(ctx, reqNor)
	checks.NoError(t, err, "CreateCompletion returned error")
	if err == nil {
		for _, c := range resp.Choices {
			t.Logf("index =`%d`,text is `%s` \n", c.Index, c.Text)
		}
	}

Prompt can be assigned string or []string type
Streaming is also supported

c := openai.NewClient("your token")
	ctx := context.Background()

	// test CreateCompletionStream
	streq := CompletionRequest{
		Model:     GPT3Curie,
		MaxTokens: 5,
		Prompt:   []string{ "a dog entered the alley", "a dog entered the alley", "a dog entered the alley"},
		Stream:    true,
	}
	stream, err := c.CreateCompletionStream(ctx, streq)
	if err != nil {
		t.Logf("CompletionStream error: %v\n", err)
		return
	}
	
	defer stream.Close()
	type index = int
	choicesMap := make(map[index]string)
	for {
		response, streamErr := stream.Recv()
		if errors.Is(streamErr, io.EOF) {
			t.Logf("CompletionBatch Stream finished")
			break
		}

		if streamErr != nil {
			checks.NoError(t, streamErr, "CompletionBatchStream error:Stream error")
		}
		t.Logf("Stream response: %#+v\n", response.Choices)
		choicesMap[response.Choices[0].Index] += response.Choices[0].Text
	}
	for k, v := range choicesMap {
		t.Logf("choice_index:%d,text:%s", k, v)
	}

[codecov]

Codecov Report

Merging #220 (d539b60) into master (b542086) will increase coverage by 0.56%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #220      +/-   ##
==========================================
+ Coverage   71.94%   72.51%   +0.56%     
==========================================
  Files          21       21              
  Lines         581      593      +12     
==========================================
+ Hits          418      430      +12     
  Misses        124      124              
  Partials       39       39              

Impacted Files	Coverage Δ
completion.go	100.00% <100.00%> (ø)
stream.go	79.31% <100.00%> (+3.31%)	⬆️

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[sashabaranov]

Thank you so much for the PR! That was a long-standing issue 🙌🏻