getAdapterName (opts) {
    opts || (opts = {})
    if (utils.isString(opts)) {
      opts = { adapter: opts }
    }
    return opts.adapter || opts.defaultAdapter
  }
Return the name of a registered adapter based on the given name or options,
or the name of the default adapter if no name provided.

@method Mapper#getAdapterName
@param {(Object|string)} [opts] The name of an adapter or options, if any.
@returns {string} The name of the adapter.
@since 3.0.0
@tutorial ["http://www.js-data.io/v3.0/docs/connecting-to-a-data-source","Connecting to a data source"]