Improve "hidden" less common configurations

# What is currently missing?

See #45

Some common configurations are not used by all implementing connectors, who need to call `hideThisConfiguration(true)` methods. This could confusing for connector developers, or fragile when new "common" configurations are added and appear unused in implementations.

We should also avoid accepting "hidden" configurations that are unused to prevent REST users from thinking they work.

# How could this be improved?

To be discussed.

# Is this a feature you would work on yourself?

* [ ] I plan to open a pull request for this feature