Adding PaymentMethod support into ApplicationContext (#237)

Author: maxzhao-bolt

const.go

@@ -102,3 +102,17 @@ const (
 	ProductCategorySoftwareOther                             ProductCategory = "OTHER"
 	ProductCategorySoftwareServices                          ProductCategory = "SERVICES"
 )
+
+type PayeePreferred string // Doc: https://developer.paypal.com/api/orders/v2/#definition-payment_method
+const (
+	PayeePreferredUnrestricted 						PayeePreferred = "UNRESTRICTED"
+	PayeePreferredImmediatePaymentRequired 					PayeePreferred = "IMMEDIATE_PAYMENT_REQUIRED"
+)
+
+type StandardEntryClassCode string // Doc: https://developer.paypal.com/api/orders/v2/#definition-payment_method
+const (
+	StandardEntryClassCodeTel					StandardEntryClassCode="TEL"
+	StandardEntryClassCodeWeb					StandardEntryClassCode="WEB"
+	StandardEntryClassCodeCcd					StandardEntryClassCode="CCD"
+	StandardEntryClassCodePpd					StandardEntryClassCode="PPD"
+)

types.go

@@ -198,11 +198,18 @@ type (
 		Locale             string             `json:"locale,omitempty"`
 		ShippingPreference ShippingPreference `json:"shipping_preference,omitempty"`
 		UserAction         UserAction         `json:"user_action,omitempty"`
+		PaymentMethod	   PaymentMethod      `json:"payment_method,omitempty"`
 		//LandingPage        string `json:"landing_page,omitempty"` // not found in documentation
 		ReturnURL string `json:"return_url,omitempty"`
 		CancelURL string `json:"cancel_url,omitempty"`
 	}
 
+	// Doc: https://developer.paypal.com/api/orders/v2/#definition-payment_method
+	PaymentMethod struct {
+		PayeePreferred	  		PayeePreferred      	`json:"payee_preferred,omitempty"`
+		StandardEntryClassCode	        StandardEntryClassCode  `json:"standard_entry_class_code,omitempty"`
+	}
+
 	// Authorization struct
 	Authorization struct {
 		ID               string                `json:"id,omitempty"`