openai[minor]: Add support for json schema response format

[bracesproul]

port of https://github.com/langchain-ai/langchain/pull/25123/files

Closes #6477
Closes #6479

Requires a release of @langchain/core and bumping min core version of oai

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[david8z]

Hello @bracesproul is there any example on how should this be used?

[david8z]

Hello @bracesproul is there any example on how should this be used?

Got it working:

const model = new ChatOpenAI({
  model: "gpt-4o-mini",
}).bind({
  response_format: {
    type: "json_schema",
    json_schema: {
      name: "schemaName",
      schema: zodSchema,
    },
  },
});

const parser = StructuredOutputParser.fromZodSchema(zodSchema);
const typedResponse = await prompt.pipe(model).pipe(parser)

[bracesproul]

@david8z sweet! I also have an example here showing how to use it with withStructuredOutput

[nguyenthinhit996]

Hi @bracesproul , nice to meet you. I'm currently working on LangChain.js with the Gmail Toolkit (specifically GmailCreateDraft), along with LangSmith and OpenAI. I noticed an issue with the function calling when using optional fields defined with Zod. Although fields like cc and bcc are marked as optional in the toolkit, it seems that the function is requiring all fields to be included. After investigating, I found that the zodToJsonSchema function automatically inserts some default values, which causes the resulting JSON schema to not align with the expected requirements.