typeorm: Saving multiple entities with related objects at the same time does not work with cascade = true

Issue type:

[ ] question [x] bug report [ ] feature request [ ] documentation issue

Database system/driver:

[ ] cordova [ ] mongodb [ ] mssql [ ] mysql / mariadb [ ] oracle [x] postgres [ ] sqlite [ ] sqljs [ ] websql

TypeORM version:

[ ] latest [x] @next [ ] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:

Repository to reproduce the issue: https://github.com/darkbasic/typeorm-repro2

const chat1 = new Chat({
  allTimeMembers: [user1, user5],
  listingMembers: [user1, user5],
});
await connection.manager.save(chat1);

await connection.manager.save([
  new Message({
    chat: chat1,
    sender: user1,
    content: 'I should buy a boat',
    type: MessageType.TEXT,
    holders: [user1, user5],
    recipients: [
      new Recipient({
        user: user5,
      }),
    ],
  }),
  new Message({
    chat: chat1,
    sender: user1,
    content: 'You still there?',
    type: MessageType.TEXT,
    holders: [user1, user5],
    recipients: [
      new Recipient({
        user: user5,
      }),
    ],
  })
]);

If I save more entities at the same time (each one with realated objects and cascade set to true) it silently fails to insert them (it inserts only one of them).

The same exact code split into diffent calls works flawlessly:

const chat1 = new Chat({
  allTimeMembers: [user1, user5],
  listingMembers: [user1, user5],
});
await connection.manager.save(chat1);

await connection.manager.save(new Message({
  chat: chat1,
  sender: user1,
  content: 'I should buy a boat',
  type: MessageType.TEXT,
  holders: [user1, user5],
  recipients: [
    new Recipient({
      user: user5,
    }),
  ],
}));

await connection.manager.save(new Message({
  chat: chat1,
  sender: user1,
  content: 'You still there?',
  type: MessageType.TEXT,
  holders: [user1, user5],
  recipients: [
    new Recipient({
      user: user5,
    }),
  ],
}));