feat: use dedicated fragments for AGW token generation

[NicoleMGomes]

PR recreated from contrib #110 extended with tests

Description

Adding token fetching based on dedicated AGW fragments for the AGW client. Additionally it exposes the URL of AGW as fetched from the fragment.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Dependency update

How to Test

1. Use an agent that has the new fragment generation applied
2. Make sure that these fragments were created for your test tenant
3. Do a regression test of the existing client functionality
4. Also test whether the standalone auth fetching functions work and return valid tokens + URLs

Checklist

Before submitting your PR, please review and check the following:

• I have read the Contributing Guidelines
• I have verified that my changes solve the issue
• I have added/updated automated tests to cover my changes
• All tests pass locally
• I have verified that my code follows the Code Guidelines
• I have updated documentation (if applicable)
• I have added type hints for all public APIs
• My code does not contain sensitive information (credentials, tokens, etc.)
• I have followed Conventional Commits for commit messages

[prashantrakheja]

looks good, tested customer flow with system credentials, minor comments