Avoid counter-intuitive default values in applicative parsers

[KtorZ]

Our command-line option parsers all have default values, which in many cases do not make a lot of sense. This is the case, for example, of the cardanoSigningKeyFileParser which will default to "cardano.sk"

This is counter-intuitive and we should only provide default values when the defaults are sensible.

[pgrange]

Based on my former operating experience, I would suggest we don't set any default value at all for any of the parameters (except when it really makes sense).

When you've managed to code all your infrastructure, test everything and have a top-notch monitoring in place. The last thing that generally falls between the cracks is misconfiguration. A classic one, while promoting an artefact from staging to production being oups, we forgot to setup this configuration parameter on production environment.

In that kind of situation, I would always prefer seeing the application crash with an explicit message about what part of the configuration is missing rather than having it run on a default value and not knowing that something's shady is happening on production.

[ch1bo]

Let's update the original description with some concrete thing What we want to do and adopt it into the roadmap? :)

[ch1bo]

Tracked in #1064