[Container] Heads-up: All Azure CLI modules need to be migrated to track 2 SDK due to track 1 SDK's retirement

Hi Jan,
    This is a heads-up that all Azure CLI modules need to be migrated from track 1 SDK to track 2 SDK because track 1 is in sunset and will be retired soon (track 2 is the future).
    You receive this message because your team owns `Container` module in Azure CLI. (Your team need do the migration work, but we’ll help you if you encounter any questions or issue during migration.)

    Here is the timeline for track 1 SDK retirement,
- Maintenance period: After July 2021, all new features will only be supported in track 2 SDK and only security and bug fix for track 1 SDK. If you want to develop new features in Azure CLI after July 2021, you must migrate to track 2 SDK by that time.
- Official retirement: After Feb 2022, will submit Azure Global request for track 1 SDK official retirement.

    Based on the timeline above, we propose your team migrates Container to track 2 SDK ASAP.
    You can follow our migration guidance during your migration.
    If any suggestions/concerns about the migration, please let us know.