Move Dashboard::Manager out of app/registries/ to permit autoloading
Dashbaord::Manager has always been excluded from autoloading as it kept a list of known widgets in a class variable. In #10927, it was moved to app/registries/ to preserve this status and keep it from being autoloaded.
It is possible to rewrite this class in an autoload-friendly manner, where the list of builtin widgets is hardcoded inside the class and then the total list of default widgets is retrieved from Foreman::Plugin when required, instead of plugins appending to the dashboard class variable.
- Allow the source file to be kept in app/services/, easier for people to find
- Allow the class to be reloaded in development, so changes to builtin widgets are immediately visible
- Allow initialisation to be removed from config/initializers/, speeding up the application load time
- Make the class more testable, by removing modifications to class variables
fixes #19464 - rewrite Dashboard::Manager to support autoloading
Replaces class-level widget storage with a static list of built-in
widgets, then appends the registered plugin widgets to get the full
default list of widgets. As a result, the class can safely be reloaded
when modified and is more testable as class-level state is removed.