The ViewEngine message extraction generated a variety of legacy formats
for extracted message ids. These formats have a number of issues related
to whitespace handling and reliance upon information inside the original
HTML of a template. The new message format is more resilient, and can be
generated directly from calls to `$localize`. This allows messages in
application code to have the same id as identical messages in templates.
As a first step in migrating projects away from the legacy id format
for i18n messages, newly generated projects now turn off the legacy ids.
See https://github.com/angular/angular-cli/pull/19232.
This commit updates the documentation to include information about this
option, since it is now publicly exposed in new CLI projects.
PR Close#39453
fdb6b98d80