Ability to use only per-type DefaultIndices dictionary, without setting global DefaultIndex at all

[maximpashuk]

Hi.

I have metadata-like dictionary, which maps document type to its index name.
It maps greatly on DefaultIndeces property of ConnectionSettings class.
Since I always work with strongly-typed API, there is no need for me to set global DefaultIndex property at all.
I can always get index name from metadata dictionary

But If you take a look at
https://github.com/Mpdreamz/NEST/blob/master/src/Nest/Resolvers/IndexNameResolver.cs

You will see that GetIndexForType method always touches DefaultIndex property, and touching this propery throws an exception "No default index set on connection!" if I not set it.

If it is will not get any troubles, can this part of code be rewritten without touching DefaultIndex property if DefaultIndices already contains index name?

Something like this:

        public string GetIndexForType(Type type)
        {
            var defaultIndices = this._connectionSettings.DefaultIndices;
            if (defaultIndices != null && defaultIndices.ContainsKey(type) && !string.IsNullOrWhiteSpace(defaultIndices[type]))
            {
                return defaultIndices[type]
            }

            return this._connectionSettings.DefaultIndex;
        }

Sorry for issue instead of pull request.

[Mpdreamz]

Good catch, this seems like a better default behaviour if you go the all typed route.

[maximpashuk]

Will you include my suggestion in 0.11.6 ?