Merge external provider identities on backend

Hello,

We have many users that authenticated with Facebook, Google or User Pool.
Some users got an expired session after a while and forgot which method they used previously and end up re-creating an account with another provider which may have the same email address.

I want to run a backend script which will merge the identities of my users having the same emails.

However, it looks like it's impossible and this can only be done with developer authenticated identities. So from what I read I can't merge a FB and Google identities on my own even as the IdentityPool owner.

Am I missing something? Is this something that could be done?
I can't initiate the merge from the client side as the session from previous provider is already lost.

I have around 20% of identities that are "duplicates" pointing to the same user ... my client wants this merged/cleaned.

What can I do?

Thank you
nicolas

Edited by: koxprod on Apr 28, 2019 4:07 PM