Merge branch '4.0' of https://github.com/silverstripe/silverstripe-mfa into 4.0

Author: Garion Herman

composer.json

@@ -37,6 +37,9 @@
         "phpunit/phpunit": "^5.7",
         "squizlabs/php_codesniffer": "^3.0"
     },
+    "conflict": {
+        "silverstripe/subsites": "<2.3.1"
+    },
     "suggest": {
         "silverstripe/totp-authenticator": "Adds a method to authenticate with you phone using a time-based one-time password.",
         "silverstripe/webauthn-authenticator": "Adds a method to authenticate with security keys or built-in platform authenticators."