Configure merge train to update Security master with Canonical master

As part of #1018 (closed), we need to update security master with canonical master through Merge Train.

We need to ensure that:

  • Merge train is executed on every new commit on Master canonical
  • If there are conflicts when merging:
    • Manual intervention from Release Manager will be required. In this case, the merge train needs to fail loudly when there’s a conflict during security merge, rather than the ours strategy
    • A notification is posted on the #g_delivery channel.
Edited by Mayra Cabrera