Staging->Main

See merge request !52

Production updates

See merge request !50

Deployment on main

See merge request !47

Deployment from main

See merge request !45

updated logic of the test-job

See merge request !39

Updating main to reflect staging

See merge request !37

updated logic of the test-job

See merge request !31

* updated workflow rules
* updated job names
* updated container versions
* added a template for gke-initialization

* app's frontend and backend are combined and served together from Node.js

* add code block to demonstrate build process in a more readable way
  (other than the Makefile)
* emphasise the sensitivity of the JWT token

* NodeJS: v16
* NPM: v8
* Jest: v27
* Mongoose: v6

And fix some small issues along the way

APP_NODE_MODULE_DIRS contains two paths. Quoting that var breaks
the command and the node_module folders were not deleted.

* remove 'renders a todo add' test since it was a) the wrong place
  and b) already implemented by PR #36
* fix indentation and make sure that there is actually a user that
  the test tries to delete

* bump NPM from v6 to v7
* regenerated package lock files
* bump Node from v12 to v14

* changed the way how the paths of makefile and .local folder are determined
* removed failsafe and replaced it with quoted path variables