feat: add optional student nickname for informal display

Keep legal first and last names for formal lists; show DisplayFirstName on teams, calendars, and import matching so two Josiahs can be told apart.

Co-authored-by: Cursor <cursoragent@cursor.com>

Core/Parsers/AssignmentRequirementParser.cs

@@ -9,6 +9,10 @@ public class AssignmentRequirementParser : CsvParserBase
 	{
 	}
 
+	public AssignmentRequirementParser(StreamReader reader, bool ignoreBlankLines = true) : base(reader, ignoreBlankLines)
+	{
+	}
+
 	public AssignmentRequirement[] Parse(ICollection<EventDefinition> events, ICollection<Student> students)
 	{
 		var assumptions = new List<AssignmentRequirement>();
@@ -20,7 +24,11 @@ public class AssignmentRequirementParser : CsvParserBase
 
 		var studentArray = 
             studentColumns
-                .Select(c => students.FirstOrDefault(s => s.FirstName == c)).ToArray();
+                .Select(c => students.FirstOrDefault(s =>
+                    string.Equals(s.DisplayFirstName, c, StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(s.Nickname, c, StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(s.FirstName, c, StringComparison.OrdinalIgnoreCase)))
+                .ToArray();
 
 		while (CsvReader.Read())
 		{