Generate API paths without leading forward slash (#3700)

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))
 {