Add random noise to passenger count data

[mjaakko]

Add random noise to passenger count data to better preserve passenger privacy. Currently passenger count data is published as an enum value (EMPTY, FEW_SEATS_AVAILABLE, etc.). When the value changes, it is possible to detect individual passengers boarding or alighting the vehicle. Add random noise (e.g. ±5%) to the raw vehicle load ratio and calculate the enum value from this.

This change should be done so that Reittiloki will display the same passenger count values

[mjaakko]

Some work was already done:
https://github.com/HSLdevcom/transitdata-common/tree/feat/randomized_passenger_count
https://github.com/HSLdevcom/transitdata-hfp-parser/tree/feat/randomized_load_ratio
https://github.com/HSLdevcom/transitlog-apc-sink/tree/feat/randomized_load_ratio
https://github.com/HSLdevcom/transitdata-vehicleposition-processor/tree/feat/random_passenger_count

[mjaakko]

Waltti might have a more robust solution for this, done in cooperation with University of Helsinki. See #topic-waltti-apc channel in Slack for discussion

[teemu8655]

Helsinki university anonymizer is done https://github.com/DPBayes/apc-anonymizer