message: feat(backend): allow anyone to add markers to datastore
diff: rules_version = '2';
  +function verifyMarkerDataComplete(data) {
  + return ('contentTitle' in data) &&
  + ('type' in data) &&
  + ('type' in data.type) &&
  + ('contact' in data) &&
  + ('loc' in data) &&
  + ('description' in data.loc) &&
  + ('lat' in data.loc) &&
  + ('lng' in data.loc) &&
  + ('serviceRadius' in data.loc)
  +}
  +
  function isAuthenticated() {
  return request.auth.uid != null;
  }
  @@ -126,6 +138,14 @@ service cloud.firestore {
  allow read, write: if false;
  }
  + match /markers/{markerID} {
  + // Anyone can read any marker
  + allow read: if true;
  + // Any one can add a marker (but not edit it)
  + allow write: if verifyMarkerDataComplete(request.resource.data) &&
  + !exists(/databases/$(database)/documents/markers/$(request.resource.id));
  + }
  +
  match /users/{userID} {
  // Anyone can read your profile
  allow read: if isAuthenticated();
  