insertPlaybookRegistration function
Adds '<name>': <className>.new, to the playbooks map in file.
Returns the updated file, or null when the playbook is already registered
or the playbooks map can't be found.
Implementation
String? insertPlaybookRegistration(
String file, {
required String name,
required String className,
}) => insertRegistryEntry(
file,
variable: 'playbooks',
type: 'Playbook Function()',
key: name,
value: '$className.new',
);