Secure write back possible in custom visual?

Hi PowerBI community,

I have a question:
- Is it possible to -in a secure way- implement write back functionality in PowerBI using custom visuals?
- if so, how?
- if not, please explain what the blocking piece is

Details
- please note that I have already a working .pbiviz that does write back functionality (it can call an external api using jQuery). I have verified that I was able to post datapoints from powerbi to this api that is hosted on a different server

Only question is security related
- Now this external api is “open”: no authentication required
- My question is if (and how) I can authenticate myself against this external api so only authenticated users in PowerBI can call the apu

Use case
- we have a clients that have this requirement, and are flexible in how to exactly organize this

Please let me know what is (or is not) possible

Thanks!