Add examples for attachments in swagger doc

Author: AchoArnold

api/pkg/entities/message.go

@@ -90,7 +90,7 @@ type Message struct {
 	UserID      UserID         `json:"user_id" gorm:"index:idx_messages__user_id" example:"WB7DRDWrJZRGbYrv2CKGkqbzvqdC"`
 	Contact     string         `json:"contact" example:"+18005550100"`
 	Content     string         `json:"content" example:"This is a sample text message"`
-	Attachments pq.StringArray `json:"attachments" gorm:"type:text[]" swaggertype:"array,string"`
+	Attachments pq.StringArray `json:"attachments" gorm:"type:text[]" swaggertype:"array,string" example:"https://example.com/image.jpg,https://example.com/video.mp4"`
 	Encrypted   bool           `json:"encrypted" example:"false" gorm:"default:false"`
 	Type        MessageType    `json:"type" example:"mobile-terminated"`
 	Status      MessageStatus  `json:"status" example:"pending"`

api/pkg/requests/message_send_request.go

@@ -19,7 +19,7 @@ type MessageSend struct {
 	Content string `json:"content" example:"This is a sample text message"`
 
 	// Attachments are optional. When you provide a list of attachments, the message will be sent out as an MMS
-	Attachments []string `json:"attachments" validate:"optional"`
+	Attachments []string `json:"attachments" validate:"optional" example:"https://example.com/image.jpg,https://example.com/video.mp4"`
 
 	// Encrypted is an optional parameter used to determine if the content is end-to-end encrypted. Make sure to set the encryption key on the httpSMS mobile app
 	Encrypted bool `json:"encrypted" example:"false" validate:"optional"`