Get a customer by ID

{  "name": "TechStart Solutions",  "external_id": "5eb02857-a71e-4ea2-bcf9-1753826282",  "email": "finance@techstart.io",  "address": {    "line1": "123 Innovation Way",    "line2": "Suite 400",    "city": "San Francisco",    "state": "CA",    "postal_code": "94087",    "country": "US"  },  "phone": "+1 (555) 789-1234",  "payment_method_token": "6ta69628uw121251c",  "payment_method_type": "CARD",  "metadata": [    {      "key": "Purchase Order",      "value": "PO-2023-4521",      "display_in_invoice": true    },    {      "key": "Sales Region",      "value": "West Coast",      "display_in_invoice": false    }  ],  "id": "f772b19c-c5c2-426d-8871-346a6cd094c5"}