Added support for button property (#175)

Author: manjurulhoque

.gitignore

@@ -4,6 +4,7 @@
 *.dll
 *.so
 *.dylib
+.idea
 
 # Test binary, built with `go test -c`
 *.test

const.go

@@ -60,6 +60,7 @@ const (
 	PropertyTypeStatus         PropertyType = "status"
 	PropertyTypeUniqueID       PropertyType = "unique_id"
 	PropertyTypeVerification   PropertyType = "verification"
+	PropertyTypeButton         PropertyType = "button"
 )
 
 const (

object.go

@@ -212,3 +212,6 @@ type Verification struct {
 	VerifiedBy *User             `json:"verified_by,omitempty"`
 	Date       *DateObject       `json:"date,omitempty"`
 }
+
+type Button struct {
+}

property.go

@@ -393,6 +393,20 @@ func (p VerificationProperty) GetType() PropertyType {
 	return p.Type
 }
 
+type ButtonProperty struct {
+	ID     ObjectID     `json:"id,omitempty"`
+	Type   PropertyType `json:"type,omitempty"`
+	Button Button       `json:"button"`
+}
+
+func (p ButtonProperty) GetID() string {
+	return p.ID.String()
+}
+
+func (p ButtonProperty) GetType() PropertyType {
+	return p.Type
+}
+
 type Properties map[string]Property
 
 func (p *Properties) UnmarshalJSON(data []byte) error {
@@ -485,6 +499,8 @@ func decodeProperty(raw map[string]interface{}) (Property, error) {
 		p = &UniqueIDProperty{}
 	case PropertyTypeVerification:
 		p = &VerificationProperty{}
+	case PropertyTypeButton:
+		p = &ButtonProperty{}
 	default:
 		return nil, fmt.Errorf("unsupported property type: %s", raw["type"].(string))
 	}