add: Support send_each_at mail header

helpers/mail/mail_v3.go

@@ -52,6 +52,7 @@ type Personalization struct {
 	DynamicTemplateData map[string]interface{} `json:"dynamic_template_data,omitempty"`
 	Categories          []string               `json:"categories,omitempty"`
 	SendAt              int                    `json:"send_at,omitempty"`
+	SendEachAt          []int                  `json:"send_each_at,omitempty"`
 }
 
 // Email holds email name and address info
@@ -369,6 +370,11 @@ func (p *Personalization) SetSendAt(sendAt int) {
 	p.SendAt = sendAt
 }
 
+// SetSendEachAt ...
+func (p *Personalization) SetSendEachAt(sendEachAt []int) {
+	p.SendEachAt = sendEachAt
+}
+
 // NewAttachment ...
 func NewAttachment() *Attachment {
 	return &Attachment{}

helpers/mail/mail_v3_test.go

@@ -380,6 +380,18 @@ func TestV3PersonalizationSetSendAt(t *testing.T) {
 	assert.Equal(t, sendAt, p.SendAt, fmt.Sprintf("sendat should be %d, got %d", sendAt, p.SendAt))
 }
 
+func TestV3PersonalizationSetSendEachAt(t *testing.T) {
+	sendAts := []int{
+		time.Now().Second(),
+		time.Now().AddDate(0, 0, 1).Second(),
+	}
+
+	p := NewPersonalization()
+	p.SetSendEachAt(sendAts)
+
+	assert.Equal(t, len(sendAts), len(p.SendEachAt), fmt.Sprintf("length of SendEachAt should be %d, got %d", len(sendAts), len(p.SendEachAt)))
+}
+
 func TestV3NewAttachment(t *testing.T) {
 	assert.NotNil(t, NewAttachment(), "NewAttachment() shouldn't return nil")
 }