Idea: Add some kind of "invariant" (or whatever it should be called) as a shortcut for placing a constraint on self.value()

[maxkratz]

Example:

constraint -> mapping::aom {
	[self.variables().hours + self.variables().overTime >= 1 =>
	self.value() >= 1] & 
	[self.value() >= 1 =>
	self.variables().hours + self.variables().overTime >= 1]
}

Possible shortcuts/syntactic sugar:

invariant -> mapping::aom {
	self.variables().hours + self.variables().overTime >= 1
}

constraint -> mapping::aom {
	inv: self.variables().hours + self.variables().overTime >= 1
}

// Maybe "invariant" or "inv" is not completely correct -> we should choose another name

Currently, the longer form of this expression can be written as a boolean equivalence:

constraint -> mapping::aom {
	self.variables().hours + self.variables().overTime >= 1 <=> self.value() >= 1
}