NEW Only get an authenticator if it's an object

[indygriffiths]

Use-case: if a module is defining its own authenticator and you want to disable it, as it seems we don't have Authenticator::unregister_authenticator() anymore in SS4 and I can't spot how to remove YAML-based injected properties, then this lets you mark it as null or false to stop it from being used. Without this code fix it errors out when it attempts to call supportedServices()

Example YAML config

---
Name: removemoduleauthenticator
After:
  - 'moduleauthenticator'
---
SilverStripe\Core\Injector\Injector:
  SilverStripe\Security\Security:
    properties:
      Authenticators:
        SomeAuthenticatorProvidedByAModule: false

If you can un-define a property in YAML, I humbly withdraw this PR if it's not needed 😄

[robbieaverill]

So the config layer lets you unset YAML values like this already, but I think because this is specifically pushing values into an injected property that it doesn't filter it out. I originally thought that we could filter falsy values out in Injector itself, but that would be wrong because you might actually want to have them.

One suggestion I might have is to use array_filter in getAuthenticators(), use that in hasAuthenticator() instead of the prop directly, then you could probably get away with a one line change instead

[kinglozzer]

Yeah I’ve come across this issue before when trying to replace the core authenticator instead of adding a second one. We worked around it with YAML: https://github.com/bigfork/silverstripe-oauth-login#replacing-the-default-authenticator

Adding array_filter to either getAuthenticators()/setAuthenticators() sounds good to me

[robbieaverill]

Retrospective approval - nice :)