Avoid branch for separator for enumerable path parameters

Assuming configured array types will implement System.Collections.Generic.IEnumerable<T>, use
IEnumerator<T> directly to add separator before any but the first item of an enumerable path
parameter.

Author: Khyalis

src/NSwag.CodeGeneration.CSharp/Templates/Client.Class.PathParameter.liquid

@@ -1,35 +1,50 @@
 {% if parameter.IsDateTimeArray -%}
+using (var enumerator = {{ parameter.VariableName }}.GetEnumerator())
 {
-    bool isAfterFirst = false;
-    foreach (var item in {{ parameter.VariableName }})
+    if (enumerator.MoveNext())
     {
-        if (isAfterFirst) urlBuilder_.Append(',');
-        urlBuilder_.Append(System.Uri.EscapeDataString(item.ToString("{{ ParameterDateTimeFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
-        isAfterFirst = true;
+        urlBuilder_.Append(System.Uri.EscapeDataString(enumerator.Current.ToString("{{ ParameterDateTimeFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
+
+        do
+        {
+            urlBuilder_.Append(',');
+            urlBuilder_.Append(System.Uri.EscapeDataString(enumerator.Current.ToString("{{ ParameterDateTimeFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
+        }
+        while (enumerator.MoveNext());
     }
 }
 {% elsif parameter.IsDateArray -%}
+using (var enumerator = {{ parameter.VariableName }}.GetEnumerator())
 {
-    bool isAfterFirst = false;
-    foreach (var item in {{ parameter.VariableName }})
+    if (enumerator.MoveNext())
     {
-        if (isAfterFirst) urlBuilder_.Append(',');
-        urlBuilder_.Append(System.Uri.EscapeDataString(item.ToString("{{ ParameterDateFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
-        isAfterFirst = true;
+        urlBuilder_.Append(System.Uri.EscapeDataString(enumerator.Current.ToString("{{ ParameterDateFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
+
+        do
+        {
+            urlBuilder_.Append(',');
+            urlBuilder_.Append(System.Uri.EscapeDataString(enumerator.Current.ToString("{{ ParameterDateFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
+        }
+        while (enumerator.MoveNext());
     }
 }
 {% elsif parameter.IsDateTime -%}
 urlBuilder_.Append(System.Uri.EscapeDataString({{ parameter.VariableName }}.ToString("{{ ParameterDateTimeFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
 {% elsif parameter.IsDate -%}
 urlBuilder_.Append(System.Uri.EscapeDataString({{ parameter.VariableName }}.ToString("{{ ParameterDateFormat }}", System.Globalization.CultureInfo.InvariantCulture)));
 {% elsif parameter.IsArray -%}
+using (var enumerator = {{ parameter.VariableName }}.GetEnumerator())
 {
-    bool isAfterFirst = false;
-    foreach (var item in {{ parameter.VariableName }})
+    if (enumerator.MoveNext())
     {
-        if (isAfterFirst) urlBuilder_.Append(',');
-        urlBuilder_.Append(ConvertToString(item, System.Globalization.CultureInfo.InvariantCulture));
-        isAfterFirst = true;
+        urlBuilder_.Append(ConvertToString(enumerator.Current, System.Globalization.CultureInfo.InvariantCulture));
+
+        do
+        {
+            urlBuilder_.Append(',');
+            urlBuilder_.Append(ConvertToString(enumerator.Current, System.Globalization.CultureInfo.InvariantCulture));
+        }
+        while (enumerator.MoveNext());
     }
 }
 {% else -%}