How to encrypt the lb3-model property in loopback4 application

[ian-mao]

We're migrating our loopback3 application to loopback4 by using a temporary solution of mounting it as a lb3 application under loopback4 application. But during test, we find that the model property encryption function defined by persist hook cannot be called in loopback4 application. I believe the root cause is describe in the spike story. Loopback4 do not support persist and before save.
And for workaround, I can find a solution for lb4 defined model in best practise.
But how could we handle the encryption function for mounted lb3 application?