Parametrize the package to not always need all dependencies?

[jvoigtlaender]

Concretely, these:

haskell-template-task/stack.yaml

Lines 5 to 10 in 81278a3

	- git: https://github.com/fmidue/IOTasks
	commit: 3b33001441a888ae3443def19e516e4c699fb95f
	- git: https://github.com/IagoAbal/haskell-z3
	commit: 6368e451e45359563106da7e917f6594453c5161
	- git: https://github.com/owestphal/type-match
	commit: e1afab43d2e8bfa5e2006492ed34060036e7be51

are probably only needed when one wants to do IOTasks.

Can that be "split off"?

Because it means that Z3 needs to be installed, even when one isn't going to employ it. Specifically, I assume https://github.com/fmidue/codeworld-tasks/blob/c767f250d0e599b227a31e5da0b0872ea1f9c894/README.md?plain=1#L19 is only necessary due to that. @patritzenfeld?

[patritzenfeld]

TestHelper imports IOTasks and will be compiled whether actually used in the tests or not. So I think this would need a bit more effort than just using an additional stack.yaml

[marcellussiegburg]

This should not involve separate stack.yaml files at all unless we have two conflicting libraries that should never be built together. Instead, a cabal flag (for all involved packages) should enable/prevent requiring the libraries and CPP should be used to enable/disable the imports.