tests(calendar): Add calendar render tests (#3)

- updates calendar to support overriding the current day when rendering
- supports current culture when rendering
- renames Calendar to CalendarGenerator

src/PowershellModule/Calendar/GetCalendarCommand.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Globalization;
 using System.Management.Automation;
+using ModuleCore.Calendar;
 
 namespace PowershellModule.Calendar
 {
@@ -42,7 +43,7 @@ namespace PowershellModule.Calendar
 #pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring as nullable.
 
 		// Guaranteed to be initialised in BeginProcessing. If it's not, something is cooked in some other way
-		private ModuleCore.Calendar.Calendar _calendar = null!;
+		private CalendarGenerator _calendar = null!;
 		private const string Noun = "Calendar";
 		public const string FullName = $"{VerbsCommon.Get}-{Noun}";
 
@@ -80,7 +81,7 @@ namespace PowershellModule.Calendar
 		{
 			if (dayOfWeek is null)
 			{
-				return ModuleCore.Calendar.Calendar.DefaultStartOfWeek;
+				return CalendarGenerator.DefaultStartOfWeek;
 			}
 
 			return dayOfWeek.ToLowerInvariant() switch
@@ -92,13 +93,13 @@ namespace PowershellModule.Calendar
 				"thursday" => DayOfWeek.Thursday,
 				"friday" => DayOfWeek.Friday,
 				"saturday" => DayOfWeek.Saturday,
-				_ => ModuleCore.Calendar.Calendar.DefaultStartOfWeek
+				_ => CalendarGenerator.DefaultStartOfWeek
 			};
 		}
 
 		protected override void ProcessRecord()
 		{
-			var calendar = _calendar.RenderCalendar(_dateToRender);
+			var calendar = _calendar.Render(_dateToRender);
 
 			// From _very_ basic testing, string split allocates the same as making a span and iterating over it.
 			// I'm assuming this is because a lot of the span code is what string.Split() does internally and the rest