List available custodians

{
    "custodians": [
        {
            "display_name": "Anchorage",
            "name": "anchorage",
            "status": "Active"
        },
        {
            "display_name": "BitGo Go Account",
            "enterprise_id": "enterprise-go-123",
            "name": "bitgo_go_account",
            "product_type": "go_account",
            "status": "Active"
        },
        {
            "display_name": "BitGo Custody",
            "enterprise_id": "enterprise-custody-123",
            "name": "bitgo_custody",
            "product_type": "custody",
            "status": "Active"
        }
    ]
}