feat: add env variable for enable key manager service

[ArjunKarthik]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

This PR adds env variable for enabling encryption service. Application changes for encryption service is not backward compatible, so once the build is deployed and certified stable this feature will be enabled by setting up "true" to key_manager.enabled flag. Later only application starts using encryption service for encryption and decryption. Once the config is enabled it shouldn't be disabled. Hotfix PR of #5442

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

This PR adds env variable for enabling encryption service. Application changes for encryption service is not backward compatible, so once the build is deployed and certified stable this feature will be enabled by setting up "true" to key_manager.enabled flag. Later only application starts using encryption service for encryption and decryption.

How did you test it?

This can't be tested in Test environment, since it is already enabled in both

1. key_manager.enabled: false and feature "encryption_service" disabled. Encryption and decryption happens within the application
2. key_manager.enabled: true and feature "encryption_service" disabled. Encryption and decryption happens within the application
3. key_manager.enabled: false and feature "encryption_service" enabled. Encryption and decryption happens within the application
4. key_manager.enabled: true and feature "encryption_service" enabled. Encryption and decryption happens with encryption service. Once this is enabled can't be disabled.

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code