Accuracy of data returned by Rebase Denomination

The get_rebased_value_via_usd function returns two values that help the user understand how the data was sourced: last_updated_timestamp and num_sources_aggregated. These are calculated using the maximum number of sources of each of the currency pairs and the latest of the timestamps when each of the pairs were updated.

This is a bit misleading as it does not signal to the user the risk of a stale or centralized oracle for one of the pairs. We recommend using the minimum function to calculate these values to better convey the accuracy and recency of the data to the users.