Allow runner to check service connection in background. (#3542)

* Allow runner to check service connection in background.

* .

* .

src/Sdk/DTWebApi/WebApi/ServiceConnectivityCheck.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+
+namespace GitHub.DistributedTask.WebApi
+{
+    [DataContract]
+    public class ServiceConnectivityCheckInput
+    {
+        [JsonConstructor]
+        public ServiceConnectivityCheckInput()
+        {
+            Endpoints = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        }
+
+        [DataMember(EmitDefaultValue = false)]
+        public Dictionary<string, string> Endpoints { get; set; }
+
+        [DataMember(EmitDefaultValue = false)]
+        public int IntervalInSecond { get; set; }
+
+        [DataMember(EmitDefaultValue = false)]
+        public int RequestTimeoutInSecond { get; set; }
+    }
+
+    [DataContract]
+    public class ServiceConnectivityCheckResult
+    {
+        [JsonConstructor]
+        public ServiceConnectivityCheckResult()
+        {
+            EndpointsResult = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);
+        }
+
+        [DataMember(Order = 1, EmitDefaultValue = true)]
+        public bool HasFailure { get; set; }
+
+        [DataMember(Order = 2, EmitDefaultValue = false)]
+        public Dictionary<string, List<string>> EndpointsResult { get; set; }
+    }
+}