feat: implement token generation and issuing on successful login

src/FiscalOS.Core/Identity/RefreshToken.cs

@@ -2,6 +2,22 @@ namespace FiscalOS.Core.Identity;
 
 public sealed class RefreshToken : Entity
 {
+  public string Token { get; init; } = string.Empty;
+  public DateTimeOffset ExpiresAt { get; init; }
   public Guid UserId { get; init; }
   public User User { get; init; } = new();
+
+  private RefreshToken()
+  {
+  }
+
+  public static RefreshToken From(Guid userId, string token, DateTimeOffset expiresAt)
+  {
+    return new()
+    {
+      UserId = userId,
+      Token = token,
+      ExpiresAt = expiresAt,
+    };
+  }
 }