@Override
    public boolean isReadOnly()
    {
        // If at least one provider is not readonly, neither is this proxy.
        return getUserPropertyProviders().parallelStream()
            .allMatch(UserPropertyProvider::isReadOnly);
    }
Returns whether <em>all</em> backing providers are read-only. When read-only, properties can not be created,
deleted, or modified. If at least one provider is not read-only, this method returns false.

@return true when all backing providers are read-only, otherwise false.
xmppserver/src/main/java/org/jivesoftware/openfire/user/property/UserPropertyMultiProvider.java