chg: ✨ add user-agent header with SDK and Python versions

[ianardee]

PR Details

Add a User-Agent header with SDK and Python versions, and platform.

Description

Add a new file versions.py allowing retrieving this info.

Motivation and Context

Having this info allows us to better serve our API users by letting us know which versions are in use.

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[jonathanMindee]

LGTM