curl --request GET \
  --url https://{tenantDomain}/api/v2/custom-domains/default \
  --header 'Authorization: Bearer <token>'

{
  "custom_domain_id": "cd_0000000000000001",
  "domain": "login.mycompany.com",
  "primary": false,
  "status": "ready",
  "type": "self_managed_certs",
  "is_default": false,
  "origin_domain_name": "mycompany_cd_0000000000000001.edge.tenants.auth0.com",
  "verification": {
    "methods": [
      {
        "name": "txt",
        "record": "auth0-domain-verification=...",
        "domain": "_cf-custom-hostname.login.mycompany.com"
      }
    ],
    "status": "verified",
    "error_msg": "<string>",
    "last_verified_at": "<string>"
  },
  "custom_client_ip_header": "<string>",
  "tls_policy": "recommended",
  "domain_metadata": {},
  "certificate": {
    "status": "provisioning",
    "error_msg": "<string>",
    "certificate_authority": "letsencrypt",
    "renews_before": "<string>"
  },
  "relying_party_identifier": "<string>"
}