Make user field optional in embedding request (#899)

* make user optional in embedding request

* fix unit test

batch_test.go

@@ -211,7 +211,7 @@ func TestUploadBatchFileRequest_AddEmbedding(t *testing.T) {
 					Input: []string{"Hello", "World"},
 				},
 			},
-		}, []byte("{\"custom_id\":\"req-1\",\"body\":{\"input\":[\"Hello\",\"World\"],\"model\":\"gpt-3.5-turbo\",\"user\":\"\"},\"method\":\"POST\",\"url\":\"/v1/embeddings\"}\n{\"custom_id\":\"req-2\",\"body\":{\"input\":[\"Hello\",\"World\"],\"model\":\"text-embedding-ada-002\",\"user\":\"\"},\"method\":\"POST\",\"url\":\"/v1/embeddings\"}")}, //nolint:lll
+		}, []byte("{\"custom_id\":\"req-1\",\"body\":{\"input\":[\"Hello\",\"World\"],\"model\":\"gpt-3.5-turbo\"},\"method\":\"POST\",\"url\":\"/v1/embeddings\"}\n{\"custom_id\":\"req-2\",\"body\":{\"input\":[\"Hello\",\"World\"],\"model\":\"text-embedding-ada-002\"},\"method\":\"POST\",\"url\":\"/v1/embeddings\"}")}, //nolint:lll
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

embeddings.go

@@ -155,7 +155,7 @@ const (
 type EmbeddingRequest struct {
 	Input          any                     `json:"input"`
 	Model          EmbeddingModel          `json:"model"`
-	User           string                  `json:"user"`
+	User           string                  `json:"user,omitempty"`
 	EncodingFormat EmbeddingEncodingFormat `json:"encoding_format,omitempty"`
 	// Dimensions The number of dimensions the resulting output embeddings should have.
 	// Only supported in text-embedding-3 and later models.