BTCPay Server Extensions (#1925)

* BTCPay Server Extensions

![demo](https://i.imgur.com/2S00aL2.gif)

* cleanup

* fix

* Polish UI a bit,detect when docker deployment

BTCPayServer/Extensions/StringExtensions.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace BTCPayServer
+{
+    public static class StringExtensions
+    {
+        public static string TrimEnd(this string input, string suffixToRemove,
+            StringComparison comparisonType)
+        {
+            if (input != null && suffixToRemove != null
+                              && input.EndsWith(suffixToRemove, comparisonType))
+            {
+                return input.Substring(0, input.Length - suffixToRemove.Length);
+            }
+            else return input;
+        }
+    }
+}