Add Support for Setting project_name Directly in Client Initialization

[jeffysam6]

Feature request

Right now, the Client class relies on the LANGCHAIN_PROJECT environment variable to determine the project name. However, there’s no way to directly pass a project_name when creating a Client. This can be limiting in situations where multiple projects need to be managed dynamically within the same application.

Proposed Change:
Allow Client to accept a project_name parameter during initialization. If provided, this should take priority over the LANGCHAIN_PROJECT environment variable. If not provided, the existing behavior can remain unchanged (defaulting to the environment variable).

Example:
client = Client(project_name="my-custom-project")

Motivation

Overwriting environment variables at runtime isn’t ideal, especially in multi-threaded environments. Allowing developers to pass project_name directly would make the API more flexible and easier to use without breaking current functionality.