Add CustomUid to ChatCompletionRequest

[walingcc]

Describe the change
Add CustomUid to ChatCompletionRequest

curl --location --request POST 'http://localhost:3000/api/v1/chat/completions' \
--header 'Authorization: Bearer fastgpt-xxxxxx' \
--header 'Content-Type: application/json' \
--data-raw '{
    "stream": false,
    "detail": false,
    "messages": [
        {
            "content": "Hello",
            "role": "user"
        }
    ],
    "customUid": "xxxxxx"
}'