Amazon ElastiCache | Build a generative AI Virtual Assistant with Ama…

[rlunar]

…zon Bedrock

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Description of changes: Amazon ElastiCache | Build a generative AI Virtual Assistant with Amazon Bedrock

• Fix for requirements.txt to narrow down the list of packages and created a requirements.lock for all packages
• Refactored the chatbot_app.py and chatbot_lib.py files to use dotenv package and enhance readability and docstrings.

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