Implement community area metric for taxi trips

[vingkan]

• Metric Name: taxi_pickups_2021
• Based on Table: taxitrips

Total number of taxi pickups per community area in 2021. Can also add number of dropoffs per community area.

• Where will this metric be used in the app?
  • Community Area View
• Which endpoint file should the metric be added to?
  • For community area metrics: api/endpoints/community.py

Read the documentation on how to add a new metric:

• Short Guide
• Full Guide

This task will involve at least two pull requests:

• Implement metric (possibly including unit tests)
• Publish metric (add to existing endpoint in backend and to config in frontend)

Once published, we can add another metric or move on to adding a data question in the frontend.

[vingkan]

@alkatoutl @divyashie If you prefer, you could also implement a timeline metric for number of taxi trips per day or per week, but since we only have some of the 2021 data loaded, I thought it would be good to start with a per-community area metric.