feat: Add Enterprise Managed Authorization (SEP-990) support (#1305)

tests/ModelContextProtocol.TestOAuthServer/JagTokenExchangeResponse.cs

@@ -0,0 +1,38 @@
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.TestOAuthServer;
+
+/// <summary>
+/// Represents the token exchange response for the Identity Assertion JWT Authorization Grant (ID-JAG)
+/// per RFC 8693 / SEP-990.
+/// </summary>
+internal sealed class JagTokenExchangeResponse
+{
+    /// <summary>
+    /// Gets or sets the issued JWT Authorization Grant (JAG).
+    /// Despite the field name "access_token" (required by RFC 8693), this contains a JAG JWT,
+    /// not an OAuth access token.
+    /// </summary>
+    [JsonPropertyName("access_token")]
+    public required string AccessToken { get; init; }
+
+    /// <summary>
+    /// Gets or sets the type of security token issued.
+    /// For SEP-990, this MUST be "urn:ietf:params:oauth:token-type:id-jag".
+    /// </summary>
+    [JsonPropertyName("issued_token_type")]
+    public required string IssuedTokenType { get; init; }
+
+    /// <summary>
+    /// Gets or sets the token type.
+    /// For SEP-990, this MUST be "N_A" per RFC 8693 §2.2.1 because the JAG is not an access token.
+    /// </summary>
+    [JsonPropertyName("token_type")]
+    public required string TokenType { get; init; }
+
+    /// <summary>
+    /// Gets or sets the lifetime in seconds of the issued JAG.
+    /// </summary>
+    [JsonPropertyName("expires_in")]
+    public int? ExpiresIn { get; init; }
+}