Implement WhatsApp Agent with Infobip API Integration

[sternakt]

We need to create a dedicated WhatsApp agent for the FastStream project that integrates seamlessly with the Infobip WhatsApp API. This agent should allow users of FastAgency to easily instantiate it whenever they need to add WhatsApp messaging capabilities to their applications, providing them a streamlined way to interact with clients or customers via WhatsApp.

Use example:

from fastagency.runtimes.autogen.agents.whatsapp import WhatsAppAgent

...

whatsapp_agent = WhatsAppAgent(
        name="WhatsApp_agent",
        llm_config=llm_config,
        is_termination_msg=is_termination_msg,
        whatsapp_api_key=os.getenv("WHATSAPP_API_KEY"),
    )