private static void initProvider(final Class<? extends UserProvider> clazz) {
        if (provider == null || !clazz.equals(provider.getClass())) {
            try {
                provider = clazz.newInstance();
            }
            catch (final Exception e) {
                Log.error("Error loading user provider: " + clazz.getName(), e);
                provider = new DefaultUserProvider();
            }
        }
    }
Checks if the provided address belongs to a locally registered user that potentially has not registered yet.

This method is intended to be used in use-cases where data addressed at a local user is processed, prior to that
user having received a representation in the user manager. This can occur when users are created on ad-hoc basis,
such as through the result of external authentication.

When the feature that allows future users to be considered is disabled, this method will always return false.

@param user The address of a user
@return True if the address could be used for a locally registered user, potentially not having registered yet.
xmppserver/src/main/java/org/jivesoftware/openfire/user/UserManager.java