work towards path parameters

SimpleHttpServer/Types/PathParameterAttribute.cs

@@ -0,0 +1,24 @@
+namespace SimpleHttpServer.Types;
+
+/// <summary>
+/// Specifies the name of a http endpoint path parameter. Path parameter names must be in the format $1, $2, $3, ..., and the end of the path may be $*
+/// </summary>
+[AttributeUsage(AttributeTargets.Parameter, Inherited = false, AllowMultiple = false)]
+public sealed class PathParameterAttribute : Attribute {
+    public string Name { get; }
+    public PathParameterAttribute(string name) {
+        if (string.IsNullOrWhiteSpace(name)) {
+            throw new ArgumentException($"'{nameof(name)}' cannot be null or whitespace.", nameof(name));
+        }
+
+        if (!name.StartsWith('$')) {
+            throw new ArgumentException($"'{nameof(name)}' must start with $.", nameof(name));
+        }
+
+        if (name.Contains(' ')) {
+            throw new ArgumentException($"'{nameof(name)}' must not contain spaces.", nameof(name));
+        }
+
+        Name = name;
+    }
+}