Feat/ext langgraph checkpoint

[CasperGN]

Description

Extending dapr-ext-langgraph to expand on the handling for put, put_writes and get_tuple to conform with the native LangGraph RedisSaver. This ensures that the demo's presented in the LangGraph Academy are functional.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: N/A

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[acroca]

@CasperGN Please have a look at other examples in the examples directory and follow the same pattern. Specially the following:

• The examples are runnable using mechanical markdown, you'll see the commands in the README.md. We run those files in our CI.
• You should only need requirements.txt, the python files, the components and the readme. Check for example the workflow and the demo_workflow examples as a reference.
• Hook your example in the CI, you'll find the list in the tox.ini

[CasperGN]

@acroca I've done the above and verified it runs locally with the validate.sh script.
This does however need the environment variable OPENAI_API_KEY to be present in order to run the example - how do we go about adding that?