(feat) Option to dynamically define timeframe

[Pheggas]

Hello.

Many APIs requires timeframe (from and to fields) in order to get the right response you want. As you might imagine, hardcoding timeframe is not a way to go when i want to check e.g. for bandwidth each 5 minutes.

It would be absolutely awesome to implement some naming like {{now}} and combine it like "{{now}}-15m" to get timerange from 15 minutes ago until the time of calling the API.