Sanitizing Default Error Messages in Entra External ID

I have Azure Front Door and Cloudflare set up with my Entra External ID tenant, and I call the endpoints directly using a configured custom domain, for example:

https://custom.contoso.com/{tenant-id}/signup/v1.0/start

For an invalid registration situation, the response currently displays the default Entra error message:

400 BAD REQUEST  
error_description: "AADSTS1003037: It looks like you may already have an account with us using this email address. Try signing in again with another identity provider. Trace ID: 0000-0000-0000 Correlation ID: 0000-0000-0000 Timestamp: 2026-11-03 20:12:52Z" 

Is it possible to sanitize or customize this error message in Azure Front Door or elsewhere—for invalid registrations or other events? For example:

400 BAD REQUEST

error: "invalid_request"
error_description: "The request could not be completed."