Generate a dashboard URL/token for a customer to access their billing information
curl --request GET \
--url https://api.cloud.flexprice.io/v1/portal/{external_id} \
--header 'x-api-key: <api-key>'{
"expires_at": "<string>",
"token": "<string>",
"url": "<string>"
}curl --request GET \
--url https://api.cloud.flexprice.io/v1/portal/{external_id} \
--header 'x-api-key: <api-key>'{
"expires_at": "<string>",
"token": "<string>",
"url": "<string>"
}