fix!: remove durations endpoint from p2p transfers

[tessstoddard]

Summary of Changes

• Removes durations endpoint
• Remove duration_value from recurring p2p transfer
• And add end_after_count and end_on fields to recurring p2p transfer

Based on Rev 4 changes here https://developer.mx.com/drafts/mdx/p2p_transfer/#changes-rev-1-2025-10-22

Fixes # https://mxcom.atlassian.net/browse/GCU-1198

Downstream Consumer Impact

These are breaking changes that only affect GCU connector

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works