$hadNamespace was ambiguously named, so the original PHP 8 support
update marked it true when it was strictly meant to indicate that a
namespace separator token had been encountered, resulting in bungled
parsing of complex class specs like Class(["arg" => true]).
* Add `getFieldMap` method to retrieve a list of all fields for any given class
* Add `TagsToShortcodeTask` to upgrading guide
Adding after the file migration part as this is where it makes the most sense to run it.
* `getFieldMap` accepts an array
* Move to `DataObjectSchema`
* Add `HTMLVarchar` to documentation
Minor refactoring
* Add test for checking that `subclassesfor` works without the base class
Add test `DataObjectSchema::getFieldMap` returns the correct array
* Remove cms dependency
