Restructure solution layout by module

src/__Libraries/StellaOps.Auth.Security/Dpop/DpopNonceIssueResult.cs

@@ -0,0 +1,56 @@
+using System;
+
+namespace StellaOps.Auth.Security.Dpop;
+
+/// <summary>
+/// Represents the result of issuing a DPoP nonce.
+/// </summary>
+public sealed class DpopNonceIssueResult
+{
+    private DpopNonceIssueResult(DpopNonceIssueStatus status, string? nonce, DateTimeOffset? expiresAt, string? error)
+    {
+        Status = status;
+        Nonce = nonce;
+        ExpiresAt = expiresAt;
+        Error = error;
+    }
+
+    /// <summary>
+    /// Issue status.
+    /// </summary>
+    public DpopNonceIssueStatus Status { get; }
+
+    /// <summary>
+    /// Issued nonce when <see cref="Status"/> is <see cref="DpopNonceIssueStatus.Success"/>.
+    /// </summary>
+    public string? Nonce { get; }
+
+    /// <summary>
+    /// Expiry timestamp for the issued nonce (UTC).
+    /// </summary>
+    public DateTimeOffset? ExpiresAt { get; }
+
+    /// <summary>
+    /// Additional failure information, where applicable.
+    /// </summary>
+    public string? Error { get; }
+
+    public static DpopNonceIssueResult Success(string nonce, DateTimeOffset expiresAt)
+        => new(DpopNonceIssueStatus.Success, nonce, expiresAt, null);
+
+    public static DpopNonceIssueResult RateLimited(string? error = null)
+        => new(DpopNonceIssueStatus.RateLimited, null, null, error);
+
+    public static DpopNonceIssueResult Failure(string? error = null)
+        => new(DpopNonceIssueStatus.Failure, null, null, error);
+}
+
+/// <summary>
+/// Known statuses for nonce issuance.
+/// </summary>
+public enum DpopNonceIssueStatus
+{
+    Success,
+    RateLimited,
+    Failure
+}