Refactor interface of modelling methods

[leonlan]

• [ ] The method arguments should follow the order of objects described in the docstring.

• [ ] Another issue: task vars are (op, machine) but processing times are (machine, op). Very confusing.

[leonlan]

I'm not satisfied with this method:

    def add_constraint(
        self,
        first: Operation,
        second: Operation,
        constraint: Constraint,
    ):
        """
        Adds a precedence constraint between two operations.

        Parameters
        ----------
        first
            First operation.
        second
            Second operation.
        constraint
            Constraint between the first and the second operation.
        """
        op1 = self._id2op[id(first)]
        op2 = self._id2op[id(second)]
        self._constraints[op1, op2].append(constraint)

It doesn't feel very intuitive. Instead I think we should split this up for every constraint that we have.

    def add_end_before_start(self, first: Operation, second: Operation):
        op1 = self._id2op[id(first)]
        op2 = self._id2op[id(second)]
        self._constraints[op1, op2].append(Constraint.END_BEFORE_START)

    def add_start_before_end(self, first: Operation, second: Operation):
        op1 = self._id2op[id(first)]
        op2 = self._id2op[id(second)]
        self._constraints[op1, op2].append(Constraint.START_BEFORE_END)

    def add_previous(self, first: Operation, second: Operation):
        op1 = self._id2op[id(first)]
        op2 = self._id2op[id(second)]
        self._constraints[op1, op2].append(Constraint.PREVIOUS)

    def add_same_resource(self, first: Operation, second: Operation):
        op1 = self._id2op[id(first)]
        op2 = self._id2op[id(second)]
        self._constraints[op1, op2].append(Constraint.SAME_RESOURCE)