In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.
The apiBase in .well-known/badgeconnect.json was ignored and it was
causing some failures when connecting or sending badges to an
external backpack.
For OBv2.1, it has been changed to always use the apiBase defined
in the badgeconnect.json backpack provider.
In MDL-77086 some extra information was added when a badge can't be
sent to a backpack. However, as the Badgr is not following the
specification, it's still hard to debug it when it fails (as
raised in MDL-75552, Badgr is not working because, in some cases,
it's returning the "Method Not Allowed / Request method 'POST'
not supported" error.
