message: fix(backend): only share visible markers in api
diff: import * as functions from 'firebase-functions';
  +import { FieldPath } from '@google-cloud/firestore';
  import { db } from '../../../app';
  @@ -31,7 +32,10 @@ export const data = functions.https.onRequest(async (_req, res) => {
  licenses: LICENSES,
  data: [],
  };
  - const markers = await db.collection(MARKER_COLLECTION_ID).get();
  + const markers = await db
  + .collection(MARKER_COLLECTION_ID)
  + .where(new FieldPath('visible'), '==', true)
  + .get();
  markers.forEach(doc => {
  const docData = doc.data() as IMarker;
  // TODO: add other sources (with appropriate licenses)
  