Logging Capability (#53)

* Logging Capability

* Readability

* Redundant using

---------

Co-authored-by: Stephen Toub <stoub@microsoft.com>

src/ModelContextProtocol/Protocol/Types/LoggingLevel.cs

@@ -0,0 +1,43 @@
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol.Types;
+
+/// <summary>
+/// The severity of a log message.
+/// These map to syslog message severities, as specified in RFC-5424:
+/// https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
+/// </summary>
+public enum LoggingLevel
+{
+    /// <summary>Detailed debug information, typically only valuable to developers.</summary>
+    [JsonPropertyName("debug")]
+    Debug,
+
+    /// <summary>Normal operational messages that require no action.</summary>
+    [JsonPropertyName("info")]
+    Info,
+
+    /// <summary>Normal but significant events that might deserve attention.</summary>
+    [JsonPropertyName("notice")]
+    Notice,
+
+    /// <summary>Warning conditions that don't represent an error but indicate potential issues.</summary>
+    [JsonPropertyName("warning")]
+    Warning,
+
+    /// <summary>Error conditions that should be addressed but don't require immediate action.</summary>
+    [JsonPropertyName("error")]
+    Error,
+
+    /// <summary>Critical conditions that require immediate attention.</summary>
+    [JsonPropertyName("critical")]
+    Critical,
+
+    /// <summary>Action must be taken immediately to address the condition.</summary>
+    [JsonPropertyName("alert")]
+    Alert,
+
+    /// <summary>System is unusable and requires immediate attention.</summary>
+    [JsonPropertyName("emergency")]
+    Emergency
+}