Add summary endpoints

[lvps]

For WEEE-Open/weeelab-telegram-bot#25, see WEEE-Open/tarallo#137

[Leone25]

probably better to wait since summaries are gonna get an overhaul? or are we gonna keep the end point as is for legacy and just add a second one?e

[lvps]

We just need an API for the overhauled endpoint (that returns an array), if we need a string in the client we can just join the array. So, indeed, this has to wait for the overhaul from WEEE-Open/tarallo#162