Added functionality to fetch license key from AWS Secrets Manager and SSM Parameter Store with caching

[gupta-yuvraj]

Overview

This PR introduces new functionality to support fetching New Relic license keys from multiple sources, including environment variables, AWS Systems Manager (SSM) Parameter Store, and AWS Secrets Manager. Additionally, it implements a caching mechanism to store the New Relic license key, preventing repeated fetches from Secrets Manager or SSM Parameter Store during every Lambda execution. The changes include updates to the Python source code, Terraform configuration, unit tests, and new policies for managing permissions and decryption.

Benefits

• Flexibility: Supports configuring New Relic license keys from multiple secure sources, offering greater deployment flexibility.
• Security: Utilizes AWS Secrets Manager and SSM Parameter Store, secure services for managing sensitive data.
• Performance Optimization: Adds a caching mechanism to store the New Relic license key, reducing the need for frequent fetches and improving Lambda function performance.

Additional Features

• Added the terraform variable nr_license_key_source to define the source of the license key (options: environment_var, ssm, secrets_manager) with a default value of environment_var.
• Added the terraform variable enable_caching_for_license_key to toggle caching for the New Relic license key in the Lambda function.
• Included permissions for fetching the license key from SSM Parameter Store and Secrets Manager.
• Added a policy to decrypt the license key fetched from Secrets Manager using KMS keys.

Testing

• Executed unit tests to verify that the New Relic license keys are correctly fetched from environment variables, Secrets Manager, and SSM Parameter Store.
• Validated the caching mechanism to ensure that the license key is stored and retrieved correctly without unnecessary fetch operations.
• Tested error handling for missing or invalid secrets/parameters and ensured proper decryption of the license key using KMS.