Add TimeSettings (Start, End and TTL) (#661)

* time

* .

* UT

* using JetBrains.Annotations;

src/WireMock.Net.Abstractions/Models/ITimeSettings.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace WireMock.Models
+{
+    /// <summary>
+    /// TimeSettings: Start, End and TTL
+    /// </summary>
+    public interface ITimeSettings
+    {
+        /// <summary>
+        /// Gets or sets the DateTime from which this mapping should be used. In case this is not defined, it's used (default behavior).
+        /// </summary>
+        DateTime? Start { get; set; }
+
+        /// <summary>
+        /// Gets or sets the DateTime from until this mapping should be used. In case this is not defined, it's used forever (default behavior).
+        /// </summary>
+        DateTime? End { get; set; }
+
+        /// <summary>
+        /// Gets or sets the TTL (Time To Live) in seconds for this mapping. In case this is not defined, it's used (default behavior).
+        /// </summary>
+        int? TTL { get; set; }
+    }
+}