How to update specific contact using SendGrid API - sendgrid

Question

In order to support the GDPR user's right to rectification, we need to allow our users to update their personal records.
After careful review of the SendGrid API, we didn't find an API call to update specific contact details.
SendGrid API reference: https://docs.sendgrid.com/api-reference/
For example, we want to allow the user to change an email from an old one to a new email address.
So far, we use SendGrid API to look for user records.
curl -X POST https://api.sendgrid.com/v3/marketing/contacts/search/emails \
--header "Authorization: Bearer <<YOUR_API_KEY_HERE>>" \
--data "{'emails': ['jane_doe#example.com', 'john_doe#example.com', 'joann_doe#example.com']}"
We can also load contact details if the user {id} is known.
GET GET /marketing/contacts/{id}
It will be great if someone will tell us how to update specific user details.
For example:
POST GET /marketing/contacts/{id}
Thanks

Answer 1

Twilio SendGrid developer evangelist here.
When you add or update a contact with the API the record is keyed by the email address. This means that you can't update a contact's email address directly. Instead you should delete the old contact and add a new one.

Answer 2

https://docs.sendgrid.com/api-reference/contacts/add-or-update-a-contact
If the contact already exists in the system, any entries submitted via
this endpoint will update the existing contact. The contact to update
will be determined only by the email field and any fields omitted from
the request will remain as they were. A contact's ID cannot be used to
update the contact.
As the website notes, an email address is a unique identifier for a contact and a contact can be updated with only email address. Thus you can't update a contact's email address with a new one, but may update any other fields for the contact.
Here's an example query to update an existing contact detail.
curl -X PUT 'https://api.sendgrid.com/v3/marketing/contacts' \
-H 'Authorization: <<YOUR_SENDGRID_API_KEY_HERE>>' \
-d '{"contacts": [{"email":"john_doe#example.com", "state_province_region":"CO","postal_code":"80503"}]}'