New API to return metrics per dataset per site per timebin

[nikmagini]

Currently we have APIs to:

1. get metrics per time bin per dataset, for a single site in a specific time interval (getDSdata)

2. get metrics per time bin, for a single dataset at a single site in a specific time interval (getSingleDSstat)

3. get metrics per dataset, summed over a specific time interval at a single site (DSStatInTimeWindow)

It would be convenient to have a new API to return the same information without any grouping/aggregation, i.e.:

• get metrics per time bin per dataset per site, in a specific time interval

[nikmagini]

Setting to low priority because for current studies getDSdata (with site=summary) is sufficient, since the details per site are not needed.

[nikmagini]

Another related request from Bjorn: ability to split the metrics per dataset, summed over a specific time interval at a single site (DSStatInTimeWindow) into multiple sub-intervals, using e.g. a new argument aggr=day