Enhance OpenAIModerationChain class with model_name param available for js

[VictorBenoiston]

Checked

• I searched existing ideas and did not find a similar one
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• I've clearly described the feature request and motivation for it

Feature request

I received an email two days ago from OpenAI that a few text moderation models will be deprecated.
As part of our continuous upgrade process, we are deprecating the following models. Access to these models will be shut off on October 27, 2025.
text-moderation-007
text-moderation-stable
text-moderation-latest

As this class does the text-moderation-latest under the hood, It'll most likely stop working when deprecated.

Currently, in js, we don't have a parameter to specify the model, as we do for python.

As this is becoming deprecated, I'd like to keep using langchain ecosystem, as I do throughout my entire application.

Motivation

The moderation modelas that are default by langchain for js are becoming deprecated.

Proposal (If applicable)

No response