Generate API paths without leading forward slash

This commit updates the API generator to trim the leading forward slashes from all API paths. When the base URI with which the API path will be combined also contains a relative path, the relative path should be respected in the combined URI output.

Fixes #3691

Author: russcam

src/CodeGeneration/ApiGenerator/Views/_Requests.Generated.cshtml

@@ -76,7 +76,7 @@ namespace Nest
 	public partial class @Raw(method.RequestType) @Raw(string.Format(": PlainRequestBase<{0}>, {1}", method.QueryStringParamName, method.InterfaceType))
 	{
 		protected @(Raw(method.InterfaceType)) Self => this;
-		internal static ApiUrls Urls = new ApiUrls(new [] {@Raw(string.Join(", ", method.Url.ExposedApiPaths.Select(p=>$"\"{p.Path}\"")))});
+		internal static ApiUrls Urls = new ApiUrls(new [] {@Raw(string.Join(", ", method.Url.ExposedApiPaths.Select(p=>$"\"{p.Path.TrimStart('/')}\"")))});
 		internal override ApiUrls ApiUrls => Urls;
 @foreach (Constructor c in Constructor.RequestConstructors(method, inheritsFromPlainRequestBase: true))
 {