Limit the Number of Apps

[schrieveslaach]

While there is still no way of deleting unused apps automatically (see #149), sometimes people forget to clean up there testing app and thus they occupy the resources of the backend (K8s or Docker). When there are too many applications running on any backend, people will observe weird behaviours due to swapping, container restarts, etc.

Therefore, a simple way of pretending these issues is to limit the number of applications being deployed by PREvant. Thus PREvant should offer an optional configuration option that allows people to limit the number of application being deployed.

Here should be the place to evaluate the option.

The configuration needs to take into account that there are different options (see #202) and should be implemented in such a way that you either use the limiting number or something else.