[FEATURE] Implement model, model group and connector apis

[acha5066]

Is your feature request related to a problem?

Currently I can't see a way to interact with the model apis and connectors via the php client.

What solution would you like?

Implement the apis so that I can set up connectors to 3rd party tools like OpenAI as described here: https://github.com/opensearch-project/ml-commons/blob/main/docs/remote_inference_blueprints/openai_connector_embedding_blueprint.md

A clear and concise description of what you want to happen.
Implement the Models, Connector, and Model Group APIs from https://opensearch.org/docs/latest/ml-commons-plugin/api/index/

What alternatives have you considered?

N/A

Do you have any additional context?

N/A