[RFC] Ping maintainers when module is migrated

[legalsylvain]

Context

The bot is pinging maintainers when modules are modified. that allows the maintainers to follow the changes and make sure he is aware of everything that is happening on his module.

Failing Use Case

when a contributor migrates a module, the maintainers is not pinged.

See : OCA/product-attribute#1098
Even if maintainer is defined : https://github.com/OCA/product-attribute/pull/1098/files#diff-b479b9ee04af548c59d8d408b56144c47292aa0501e12b0a40efbf22d014b94aR10

Expected behaviour

maintainers should be pinged when the modules are migrated by other contributors.