Add self-service account management commands (delete, update username/email/password/profile)

web/backend/Features/Features.Auth/Commands/UpdatePassword/UpdatePasswordHandler.cs

@@ -0,0 +1,42 @@
+using Domain.Exceptions;
+using Features.Auth.Dtos;
+using Features.Auth.Identity;
+using MediatR;
+using Microsoft.AspNetCore.Identity;
+
+namespace Features.Auth.Commands.UpdatePassword;
+
+/// <summary>
+///     Handles <see cref="UpdatePasswordCommand" /> via <see cref="UserManager{TUser}.ChangePasswordAsync" />,
+///     which verifies the current password before hashing and persisting the new one.
+/// </summary>
+public class UpdatePasswordHandler(UserManager<ApplicationUser> userManager)
+    : IRequestHandler<UpdatePasswordCommand, UpdatePasswordPayload>
+{
+    /// <exception cref="NotFoundException">Thrown when the account does not exist.</exception>
+    /// <exception cref="UnauthorizedException">Thrown when the current password does not match.</exception>
+    /// <exception cref="ConflictException">Thrown when the update otherwise fails.</exception>
+    public async Task<UpdatePasswordPayload> Handle(
+        UpdatePasswordCommand request,
+        CancellationToken cancellationToken
+    )
+    {
+        ApplicationUser user =
+            await userManager.FindByIdAsync(request.UserAccountId.ToString())
+            ?? throw new NotFoundException("User account not found");
+
+        IdentityResult result = await userManager.ChangePasswordAsync(
+            user,
+            request.CurrentPassword,
+            request.NewPassword
+        );
+        if (!result.Succeeded)
+        {
+            if (result.Errors.Any(e => e.Code == "PasswordMismatch"))
+                throw new UnauthorizedException("Current password is incorrect");
+            throw new ConflictException(string.Join("; ", result.Errors.Select(e => e.Description)));
+        }
+
+        return new UpdatePasswordPayload(user.Id, DateTime.UtcNow);
+    }
+}