fix caption for attachments not displayed once sent

ts/models/message.ts

@@ -688,6 +688,7 @@ export class MessageModel extends Backbone.Model<MessageAttributes> {
       screenshot,
       thumbnail,
       fileName,
+      caption,
     } = attachment;
 
     const isVoiceMessage =
@@ -696,6 +697,7 @@ export class MessageModel extends Backbone.Model<MessageAttributes> {
     return {
       id,
       contentType,
+      caption,
       size: size || 0,
       width: width || 0,
       height: height || 0,

ts/state/ducks/conversations.ts

@@ -136,6 +136,7 @@ export type PropsForSearchResults = {
 export type PropsForAttachment = {
   id: number;
   contentType: string;
+  caption?: string;
   size: number;
   width?: number;
   height?: number;

ts/util/attachmentsUtil.ts

@@ -109,6 +109,7 @@ export async function getFile(attachment: StagedAttachmentType, maxMeasurements?
   const scaled = await autoScale(attachment, maxMeasurements);
   const fileRead = await readFile(scaled);
   return {
+    caption: attachment.caption,
     ...fileRead,
     url: undefined,
     flags: attachmentFlags || null,