Prevent and handle code splitting errors

[incognitojam]

Read more: http://dimaip.github.io/2020/04/25/deploying-apps-with-code-splitting/

Build outputs look like this:

dist/index.html                                  1.35 kB │ gzip:  0.66 kB
dist/assets/PairActivity-BPbpkqiC.css            0.15 kB │ gzip:  0.13 kB
dist/assets/index-BLtQcLjs.css                  45.82 kB │ gzip: 12.63 kB
dist/assets/logout-6J7o6Pym.js                   0.53 kB │ gzip:  0.35 kB │ map:     0.45 kB
dist/assets/auth-CKGUWZk1.js                     0.73 kB │ gzip:  0.48 kB │ map:     1.29 kB
dist/assets/client-C0K2Vm7w.js                   2.09 kB │ gzip:  1.15 kB │ map:     6.09 kB
dist/assets/login-Bo5badKx.js                    3.35 kB │ gzip:  1.56 kB │ map:     7.01 kB
dist/assets/Button-BrY1xdFa.js                   3.82 kB │ gzip:  1.79 kB │ map:    10.51 kB
dist/assets/PairActivity-Cr6LpKkh.js            18.43 kB │ gzip:  6.82 kB │ map:    38.69 kB
dist/assets/qr-scanner-worker.min-D-EgXUP3.js   44.34 kB │ gzip: 10.65 kB │ map:    45.01 kB
dist/assets/index-CRJamWYb.js                  114.92 kB │ gzip: 41.12 kB │ map:   688.65 kB
dist/assets/index-t_HHjCnB.js                  211.89 kB │ gzip: 65.40 kB │ map:   864.67 kB
dist/assets/RouteVideoPlayer-u3jjkh1a.js       286.60 kB │ gzip: 90.01 kB │ map: 1,141.68 kB

If the user is browsing the app and doesn't load PairActivity-*.js yet, but we deploy an update which renames/deletes that file, when the app goes to load it there will be a JS error.

Tasks:

• CI: deploy artifacts from previous builds together with new build
  • Cloudflare may cache files for some amount of time already
• ServiceWorker: precache all JS bundles
  • Once we have PWA/ServiceWorker setup, we can use precacheAndRoute from Workbox
• fix: catch exceptions during lazy loading and force-reload app
  • does not preserve state, but last resort