Fix authorize order to return the correct response

[binit-singh]

What does this PR do?

We are returning Authorization instead of AuthorizeOrderResponse from AuthorizeOrder() method. This PR is an attempt to fix that.

If you check the response returned from Paypal it matches with the AuthorizeOrderResponse https://developer.paypal.com/docs/api/orders/v2/#orders_authorize

	// Authorization struct
	Authorization struct {
		ID               string                `json:"id,omitempty"`
		CustomID         string                `json:"custom_id,omitempty"`
		InvoiceID        string                `json:"invoice_id,omitempty"`
		Status           string                `json:"status,omitempty"`
		StatusDetails    *CaptureStatusDetails `json:"status_details,omitempty"`
		Amount           *PurchaseUnitAmount   `json:"amount,omitempty"`
		SellerProtection *SellerProtection     `json:"seller_protection,omitempty"`
		CreateTime       *time.Time            `json:"create_time,omitempty"`
		UpdateTime       *time.Time            `json:"update_time,omitempty"`
		ExpirationTime   *time.Time            `json:"expiration_time,omitempty"`
		Links            []Link                `json:"links,omitempty"`
	}

	// AuthorizeOrderResponse .
	AuthorizeOrderResponse struct {
		CreateTime    *time.Time             `json:"create_time,omitempty"`
		UpdateTime    *time.Time             `json:"update_time,omitempty"`
		ID            string                 `json:"id,omitempty"`
		Status        string                 `json:"status,omitempty"`
		Intent        string                 `json:"intent,omitempty"`
		PurchaseUnits []PurchaseUnitRequest  `json:"purchase_units,omitempty"`
		Payer         *PayerWithNameAndPhone `json:"payer,omitempty"`
	}

Where should the reviewer start?

How should this be manually tested?

Any background context you want to provide?