Allow `max_tokens`=-1 for `ChatOpenAI` and set the default value to -1
https://github.com/hwchase17/langchain/pull/1782 Yeah it seems working well. Thank you for your feedback.
I will close this PR now.
Resolves #1532, resolves #1652.

In the current implementation of `ChatOpenAI`, the default value for max_tokens is set to 256, and it cannot take a value of -1.
In this PR, we will allow `max_tokens` to take a value of -1. When `max_tokens`=-1, the `max_tokens` parameter will be omitted, which means there will be no token limit for the response.

Originally, the default value of `max_tokens` was set to 256, causing longer responses to be cut off and creating confusion (as in issue #1652). This PR sets the default value of `max_tokens` to -1, preventing cutoffs from occurring.

The solution was originally proposed by @adlindenberg in the issue discussion (#1532). Thank you, @adlindenberg, for providing the idea for this fix.