title: Cloud Firestore - Querying for a single document based
body: <p>I am working on a project in Angular 6 using Cloud Firestore (still Firebase but not the realtime database). How do I query a collection based on a value i.e. I have a collection of users, each document in the user collection has a field called "id" which has a hash assigned to it. If I have a specific id hash in mind, how can I query the collection to get that document where the id equals the one I have in mind. Also, once I have the document, can I then obtain the document ID that was automatically assigned?</p>