Creates a dashboard in the organization. The response is the dashboard's definition; run it
with Show Dashboard.

A dashboard shows saved metrics in a layout (metrics), each at a size. Build the metrics
first: find existing ones with List Metrics, or try a definition with Preview Metric and save
it with Create Metric, then reference the IDs here. Only metrics saved in the organization can
be added; built-in metrics are shown on the built-in dashboards.

default_timeframe is the relative interval the dashboard runs over when Show Dashboard is
called without start/end. tags are the IDs of the organization's report tags.

Requests made with an API key are attributed to the user who created the key.