[local-sync] Remove isSending bit

Summary:
`isSending` was an artifact from the cloud sync engine that was used to
double check that the sending process for a multi-send draft had been
initiated. I don't believe the intermediate steps are API calls anymore,
and we've had the relevant code commented out for awhile. Time to kill it!

I've revived the double-sending tests in N1 to ensure we still have sufficient
checks against sending the draft again while the first call is still sending.
See D3834

Test Plan: N1 unit tests

Reviewers: juan, evan

Reviewed By: juan, evan

Differential Revision: https://phab.nylas.com/D3835

packages/local-sync/src/local-sync-worker/sync-worker.es6

@@ -90,7 +90,6 @@ class SyncWorker {
       where: {
         folderId: null,
         isSent: {$not: true},
-        isSending: {$not: true},
       },
     })
     const noFolderImapUID = await Message.findAll({

packages/local-sync/src/local-sync-worker/syncback-tasks/send-message-per-recipient.smtp.js

@@ -69,7 +69,6 @@ class SendMessagePerRecipientSMTP extends SyncbackTask {
     const account = this._account
 
     const baseMessage = await MessageFactory.buildForSend(db, messagePayload)
-    baseMessage.setIsSending(true)
 
     const sendResult = await sendPerRecipient({db, account, baseMessage, usesOpenTracking, usesLinkTracking})
 

packages/local-sync/src/local-sync-worker/syncback-tasks/send-message.smtp.js

@@ -24,7 +24,6 @@ class SendMessageSMTP extends SyncbackTask {
     const {messagePayload} = this.syncbackRequestObject().props
 
     const message = await MessageFactory.buildForSend(db, messagePayload);
-    message.setIsSending(true);
     const logger = global.Logger.forAccount(this._account);
     const sender = new SendmailClient(this._account, logger);
     await sender.send(message);

packages/local-sync/src/models/message.js

@@ -29,7 +29,7 @@ module.exports = (sequelize, Sequelize) => {
     // stay in sync with the current message body.
     isDraft: Sequelize.BOOLEAN,
     isSent: Sequelize.BOOLEAN,
-    isSending: Sequelize.BOOLEAN,
+    isSending: Sequelize.BOOLEAN, // Currently unused, left for potential future use
     isProcessed: { type: Sequelize.BOOLEAN, defaultValue: false },
     unread: Sequelize.BOOLEAN,
     starred: Sequelize.BOOLEAN,
@@ -109,21 +109,6 @@ module.exports = (sequelize, Sequelize) => {
         return `<${id}@nylas-mail.nylas.com>`
       },
 
-      // async findMultiSendMessage(db, messageId) {
-      //   const message = await this.findById(messageId, {
-      //     include: [
-      //       {model: db.Folder},
-      //     ],
-      //   })
-      //   if (!message) {
-      //     throw new APIError(`Couldn't find multi-send message ${messageId}`, 400);
-      //   }
-      //   if (message.isSent || !message.isSending) {
-      //     throw new APIError(`Message ${messageId} is not a multi-send message`, 400);
-      //   }
-      //   return message;
-      // },
-
       requiredAssociationsForJSON({Folder, Label, File}) {
         return [
           {model: Folder},
@@ -147,22 +132,10 @@ module.exports = (sequelize, Sequelize) => {
       setIsSent(val) {
         if (val) {
           this.isDraft = false
-          this.isSending = false
         }
         this.isSent = val
       },
 
-      setIsSending(val) {
-        if (val) {
-          if (this.isSent || this.isSending) {
-            throw new APIError('Cannot mark a sent message as sending', 400);
-          }
-          validateRecipientsPresent(this);
-          this.isDraft = false;
-        }
-        this.isSending = val
-      },
-
       fetchRaw({account, db, logger}) {
         const settings = Object.assign({}, account.connectionSettings, account.decryptedCredentials())
         return PromiseUtils.props({