PubSub name module for the MishkaCMS system.
This module serves as both the PubSub process name and a loadable module so that compile-time verifiers (e.g., MishkaGervaz) can confirm its existence.
Started by MishkaCmsCore.Application, first among its children, as:
{Phoenix.PubSub, name: MishkaCmsCore.PubSub}:mishka_cms_core is a dependency of every extension and of the host, so it is running before
any extension's application starts. A host or a test helper does not start it again: a second
child of the same name fails its supervisor's start.