Error on Quarter#GetMonths

[jlmunozcu1984]

Situation: All quarters GetMonths begin in January.
Ej:

var q2 = Quarter(2024,YearQuarter.Second);
var april = q2.GetMonths().First();
// Expected April but January returns. Same with Q3 and Q4, only Q1 works.

[Giannoudis]

Suggestion for line 98 and 99:

YearMonth startMonth;
TimeTool.AddMonth(startYear, YearBaseMonth, ((int)StartQuarter - 1) * TimeSpec.MonthsPerQuarter, out _, out startMonth);

[Giannoudis]

@jlmunozcu1984 You can add also the following unit tests:

QuarterTest.cs:

        // ----------------------------------------------------------------------
        [Trait("Category", "Quarter")]
        [Fact]
        public void QuarterGetMonthsTest()
        {
            var currentYear = ClockProxy.Clock.Now.Year;

            var q2 = new Quarter(currentYear, YearQuarter.Second);

            var months = q2.GetMonths();
            Assert.Equal(3, months.Count);
            Assert.Equal(months[0].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1));
            Assert.Equal(months[1].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1).AddMonths(1));
            Assert.Equal(months[2].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1).AddMonths(2));
        }

QuartersTest.cs:

         // ----------------------------------------------------------------------
        [Trait("Category", "Quarters")]
        [Fact]
        public void QuartersGetMonthsTest()
        {
            var currentYear = ClockProxy.Clock.Now.Year;

            var q2and3 = new Quarters(currentYear, YearQuarter.Second, 2);

            var months = q2and3.GetMonths();
            Assert.Equal(6, months.Count);
            Assert.Equal(months[0].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1));
            Assert.Equal(months[1].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1).AddMonths(1));
            Assert.Equal(months[2].Start, new DateTime(currentYear, TimeSpec.SecondQuarterMonthIndex, 1).AddMonths(2));
            Assert.Equal(months[3].Start, new DateTime(currentYear, TimeSpec.ThirdQuarterMonthIndex, 1));
            Assert.Equal(months[4].Start, new DateTime(currentYear, TimeSpec.ThirdQuarterMonthIndex, 1).AddMonths(1));
            Assert.Equal(months[5].Start, new DateTime(currentYear, TimeSpec.ThirdQuarterMonthIndex, 1).AddMonths(2));
        }