Calculator.divide throws ArithmeticException instead of a clear IllegalArgumentException for a zero divisor #1

Calculator.divide throws an unchecked ArithmeticException when the divisor is 0.

Expected behaviour: divide should validate its input and throw IllegalArgumentException with the message divisor must not be zero before performing the division.

The failing test is CalculatorTest#should_reject_division_by_zero_with_a_clear_message in src/test/java/demo/CalculatorTest.java. The method to change is in src/main/java/demo/Calculator.java. Please keep the other arithmetic methods unchanged.