Query array eager register/append

[ampatspell]

let doc = store.doc(...).new({ ... });
let cancel = this.query.append(doc);
let model = this.models.find(model => model.doc === doc);
try {
  await doc.save();
} catch(err) {
  cancel();
}

• Immediately appends doc (query array needs 2 content arrays -- live data and appended)
• register returns fn which removes doc from appended (if save fails or whatnot)
• appended docs work the same way as registered docs.
• if onSnapshot returns the same doc, it is removed from appended and moved to live data array

[ampatspell]

In addition to that, doc.delete() should also have support for this.

let model = this.models.find(model => model.id === 'foof');
let cancel = this.query.remove(doc);
// this.models.includes(model) // → false

try {
  await model.doc.delete();
} catch(err) {
  cancel();
}