I'm trying to update a contact (type = 'user') through the API, and want to populate the User ID field. I found out that in the API, this is called the External ID (which is somewhat confusing, and the docs aren't clear).
I have 2 scenarios:
Scenario 1 - all good
I create a contact through the API and directly set the External ID. The External ID shows up in the User ID field as expected. I can change this via a new API request if needed.
Scenario 2: 400 - Bad request
I create a contact through the API without setting an External ID. This works. Now, I want to update this contact and set the external ID. I get a 400 - Bad request without further details.
If I remove the External ID field from the API request, everything works and I get a 200 response.
I'm stuck with scenario 2, because I need to update contacts that I sent through the API earlier, without an external id.
More info
In both scenarios I'm making a post request and supply the Intercom ID of the contact, as well as the User Hash.