Add message

Add a message to a conversation. For inbound messages the author is assumed to be the requester of the conversation (end user). For outbound messages the author is specified using the agentId field. <br>If attachments are added to the message, they will be copied and stored in Dixa. <br> Content in outbound message is required except for Whatsapp messages. <br> Supported channels are Chat, Messenger, Contact Form, Email, Sms (outbound only), Whatsapp (outbound and Markdown only). <br><br> Supported Markdown syntax for Markdown content: bold <code>**text**</code>, italic <code>*text*</code>, bold & italic <code>***text***</code>, strikethrough <code>~text~</code>, blockquote <code> > Quoted text. \n Message about quoted text</code>, ordered list <code>List:\n1. Item\n2. Item\n3. Item</code>, unordered list <code>List:\n* Item\n* Item\n* Item</code>, inline code <code>This is `code`</code>. <br><br> Whatsapp channel: <br> Only one attachment is allowed per WhatsApp message. <br> Supports adding a message with attachment only (no content). <br> Supports the following file types for attachments: .jpg, .jpeg, .png, .pdf, .doc, .docx, .pptx, .xlsx