fix(validation): enforce DateOfBirth constraints and test coverage (#344)

- Add DateOfBirth must-be-past and >= 1900-01-01 UTC validation rules
  to PlayerRequestModelValidator
- Extract FormatBirth helper in PlayerFakes to eliminate duplicated
  birth date formatting logic across test utilities
- Add PlayerValidatorTests covering valid and invalid DateOfBirth cases

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: nanotaboada

src/Dotnet.Samples.AspNetCore.WebApi/Validators/PlayerRequestModelValidator.cs

@@ -47,7 +47,7 @@ public PlayerRequestModelValidator(IPlayerRepository playerRepository)
                 RuleFor(player => player.DateOfBirth)
                     .Must(date => date < DateTime.UtcNow)
                     .WithMessage("DateOfBirth must be a date in the past.")
-                    .Must(date => date >= new DateTime(1900, 1, 1))
+                    .Must(date => date >= new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc))
                     .WithMessage("DateOfBirth must be on or after January 1, 1900.");
             }
         );

test/Dotnet.Samples.AspNetCore.WebApi.Tests/Unit/PlayerValidatorTests.cs

@@ -212,7 +212,7 @@ public async Task GivenValidateAsync_WhenDateOfBirthIsBeforeYear1900_ThenValidat
     {
         // Arrange
         var request = PlayerFakes.MakeRequestModelForCreate();
-        request.DateOfBirth = new DateTime(1899, 12, 31);
+        request.DateOfBirth = new DateTime(1899, 12, 31, 0, 0, 0, DateTimeKind.Utc);
         var validator = CreateValidator();
 
         // Act

test/Dotnet.Samples.AspNetCore.WebApi.Tests/Utilities/PlayerFakes.cs

@@ -14,6 +14,9 @@ namespace Dotnet.Samples.AspNetCore.WebApi.Tests.Utilities;
 /// </summary>
 public static class PlayerFakes
 {
+    private static string? FormatBirth(DateTime? dateOfBirth) =>
+        dateOfBirth.HasValue ? $"{dateOfBirth.Value:MMMM d, yyyy}" : null;
+
     /// <summary>
     /// Returns the starting 11 players with generated GUIDs for in-memory testing.
     /// Reuses production player data from PlayerData.MakeStarting11().
@@ -101,7 +104,7 @@ public static PlayerResponseModel MakeResponseModelForCreate()
         {
             FullName =
                 $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-            Birth = player.DateOfBirth.HasValue ? $"{player.DateOfBirth.Value:MMMM d, yyyy}" : null,
+            Birth = FormatBirth(player.DateOfBirth),
             Dorsal = player.SquadNumber,
             Position = player.Position,
             Club = player.Team,
@@ -157,7 +160,7 @@ public static PlayerResponseModel MakeResponseModelForRetrieve(int squadNumber)
         {
             FullName =
                 $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-            Birth = player.DateOfBirth.HasValue ? $"{player.DateOfBirth.Value:MMMM d, yyyy}" : null,
+            Birth = FormatBirth(player.DateOfBirth),
             Dorsal = player.SquadNumber,
             Position = player.Position,
             Club = player.Team,
@@ -181,9 +184,7 @@ .. PlayerData
                     {
                         FullName =
                             $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-                        Birth = player.DateOfBirth.HasValue
-                            ? $"{player.DateOfBirth.Value:MMMM d, yyyy}"
-                            : null,
+                        Birth = FormatBirth(player.DateOfBirth),
                         Dorsal = player.SquadNumber,
                         Position = player.Position,
                         Club = player.Team,