Add PayPal STC API (#296)

feat: update the error details response body content (#289)

* feat: update the error details response body content

* fix: update new error response detail unit test

* fix: add Links field to ErrorResponse struct

#285 golangci lint

Signed-off-by: plutov <[email protected]>

Added url and image_url for a item (#281)

When using CreateOrder we have PurchaseUnitRequest inside it
a list of Items, according to paypal docs
https://developer.paypal.com/docs/api/orders/v2/#orders_create

this item can have a url, and a image_url

url:
The URL to the item being purchased. Visible to buyer and used in buyer experiences.

image_url:
The URL of the item's image.

Remove unused tokenservice endpoints

Fix #271

go 1.21

#263