OpenAPI Spec GPT actions: how to set Client Authentication to Send client credentials in body

Screenshot 2023-11-30 alle 11.46.13

securitySchemes:
    OAuth2AuthenticationCodeFlow:
      type: oauth2
      x-receive-token-in: request-body
      flows:
        authorizationCode:
          authorizationUrl: https://api-v2.fattureincloud.it/oauth/authorize
          tokenUrl: https://api-v2.fattureincloud.it/oauth/token
          refreshUrl: https://api-v2.fattureincloud.it/oauth/token
          scopes:
            entity.clients:r: Read permission to the Clients registry
            entity.clients:a: Write permission to the Clients registry
            entity.suppliers:r: Read permission to the Suppliers registry
            entity.suppliers:a: Write permission to the Suppliers registry
            products:r: Read permission to the Products
            products:a: Write permission to the Products
            issued_documents.invoices:r: Read permission to the issued Invoices
            issued_documents.credit_notes:r:
              Read permission to the issued Credit
              Notes
            issued_documents.receipts:r: Read permission to the issued Receipts
            issued_documents.orders:r: Read permission to the issued Orders
            issued_documents.quotes:r: Read permission to the issued Quotes
            issued_documents.proformas:r: Read permission to the issued Proformas
            issued_documents.delivery_notes:r:
              Read permission to the issued Delivery
              Notes
            issued_documents.work_reports:r: Read permission to the issued Work Reports
            issued_documents.supplier_orders:r:
              Read permission to the issued Supplier
              Orders
            issued_documents.self_invoices:r: Read permission to the issued Self Invoices
            issued_documents.invoices:a: Write permission to the issued Invoices
            issued_documents.credit_notes:a:
              Write permission to the issued Credit
              Notes
            issued_documents.receipts:a: Write permission to the issued issued Receipts
            issued_documents.orders:a: Write permission to the issued Orders
            issued_documents.quotes:a: Write permission to the issued Quotes
            issued_documents.proformas:a: Write permission to the issued Proformas
            issued_documents.delivery_notes:a:
              Write permission to the issued Delivery
              Notes
            issued_documents.work_reports:a: Write permission to the issued Work Reports
            issued_documents.supplier_orders:a:
              Write permission to the issued Supplier
              Orders
            issued_documents.self_invoices:a:
              Write permission to the issued Self
              Invoices
            received_documents:r: Read permission to the Received Documents
            received_documents:a: Write permission to the Received Documents
            stock:r: Read permission to the Stock movements
            stock:a: Write permission to the Stock movements
            receipts:r: Read permission to the Receipts
            receipts:a: Write permission to the Receipts
            taxes:r: Read permission to the Taxes
            taxes:a: Write permission to the Taxes
            archive:r: Read permission to the Archive Documents
            archive:a: Read permission to the Archive Documents
            cashbook:r: Read permission to the Cashbook
            cashbook:a: Write permission to the Cashbook
            settings:r: Read permission to the Settings
            settings:a: Write permission to the Settings
            situation:r: Read permission to the company Situation

I am using the above security scheme, but I get an error when authenticating. I tried the same openapi scheme on postman and the authentication works successfully if I use the option “Send client credentials in the body” (see screenshot above), but when I try on gpt actions it doesn’t work, I think the problem is this configuration, because changing it on postman solved the problem. I don’t know how to implement this on gpt actions