postprocess the 1min or 5min string fields

[mfa]

some fields have values written as string, i.e.

"activity": [{
"class_5min":"1112211111111111111111111111111111111111111111233322322223333323322222220000000000000000000000000000000000000000000000000000000233334444332222222222222322333444432222222221230003233332232222333332333333330002222222233233233222212222222223121121111222111111122212321223211111111111111111"
}]

here the values refer to:

0: Non-wear
1: Rest (MET level below 1.05)
2: Inactive (MET level between 1.05 and 2)
3: Low intensity activity (MET level between 2 and age/gender dependent limit)
4: Medium intensity activity
5: High intensity activity

see https://cloud.ouraring.com/docs/activity
same for hypnogram_5min in sleep data.

Convert this values to another representation for easier plotting.