​ https://firebase.google.com/docs/firestore/quickstart​
​https://medium.com/get-it-working/get-googles-firestore-working-with-react-c78f198d2364​
​https://firebase.google.com/docs/firestore/security/get-started​
// Allow read/write access on all documents to any user signed in to the applicationservice cloud.firestore {match /databases/{database}/documents {match /{document=**} {allow read, write: if request.auth.uid != null;}}}
allow read, write: if request.auth.uid != null;
service cloud.firestore {match /databases/{database}/documents {// Make sure the uid of the requesting user matches name of the user// document. The wildcard expression {userId} makes the userId variable// available in rules.match /users/{userId} {allow read, update, delete: if request.auth.uid == userId;allow create: if request.auth.uid != null;}}}
​https://firebase.google.com/docs/firestore/security/rules-conditions​
​https://firebase.google.com/docs/firestore/security/rules-query​