Refactor user creation and retrieval in tests

Updated `DbRepositoryTests` to await `CreateAsync` directly for user creation. Changed assertion to compare the created user with the user retrieved from the repository, enhancing test accuracy.

DigitalData.Core.Tests/Infrastructure/DbRepositoryTests.cs

@@ -60,10 +60,10 @@ public class DbRepositoryTests
         var user = faker.Generate();
 
         // Act
-        await _userRepo.CreateAsync(user);
+        var createdUser = await _userRepo.CreateAsync(user);
-        var createdUser = (await _userRepo.ReadAsync()).First();
+        var readUser = await _userRepo.ReadFirstOrDefaultAsync(u => u.Id == createdUser.Id);
 
         // Assert
-        Assert.That(createdUser, Is.EqualTo(user));
+        Assert.That(createdUser, Is.EqualTo(readUser));
     }
 }