Refreshes token for intellisense (#1476)

* check if token refresh needed

* add more checks

* simplify logic

* add summary and change to false

* wip

* wip

* add ExpiresOn field to check when token needs to be refreshed

* expired token check

* wip

* wip

* wip

* update expiresOn check

* wip

* wip

* working refresh token

* add closing tag

* fix summary

* pr comments

* add max tolerance

* refactoring

* refactoring and updating descriptions

* remove comment

* pr updates

* more pr comments

* pr comments

* wip

* pr comments - add state tracker

* update comment

* fix type

* pr comments

* fix race condition

* wip

* pr comments

* add comment

* pr comments

* nullable int

* pr comments

* remove uri from map upon disconnect

* pr comments

* remove uri from map upon editor close

* pr comments

src/Microsoft.SqlTools.ServiceLayer/Connection/Contracts/ConnectionDetails.cs

@@ -543,7 +543,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection.Contracts
                 SetOptionValue("databaseDisplayName", value);
             }
         }
-
+        
         public string AzureAccountToken
         {
             get
@@ -556,6 +556,18 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection.Contracts
             }
         }
 
+        public int? ExpiresOn
+        {
+            get
+            {
+                return GetOptionValue<int?>("expiresOn");
+            }
+            set
+            {
+                SetOptionValue("expiresOn", value);
+            }
+        }
+
         public bool IsComparableTo(ConnectionDetails other)
         {
             if (other == null)