Immutable Query objects

@JanHolger arbeitet bereits daran.

Seit 13.9.2023.

**Is your feature request related to a problem? Please describe.**
Right now the Query and QueryGroup classes are built in a builder pattern style way (mutating their own object and returning this). This has a couple advantages but also comes with several disadvantages and I would generally say that it is bad practice.

**Describe the solution you'd like**
Since completely changing them to immutable may break existing code and may not be in favor of all users, I would rather add a new .mutable() and .immutable() switch and a default state for new queries in the config.