costerra v0.2.0

Added

• Observed usage: when the credentials allow it, the last 30 days of Cloud
  Monitoring metrics (VM CPU and uptime, bucket and Cloud SQL storage, Cloud
  Run requests) fill the usage keys the usage file does not set, and active
  Compute Engine commitments are taken into account. Optional, cached for
  6 hours; --no-observed, COSTERRA_NO_OBSERVED or observed_usage: false
  turn it off. A Usage line shows how many resources were observed, and
  notes say which permissions are missing.
• Data-based rules: compute-idle, compute-rightsize and
  compute-schedule-nonprod.
• Every recommendation says what it is based on (basis in JSON: code,
  usage_file or observed).

Changed

• Commitment advice leaves out vCPUs already covered by active commitments,
  and cheaper machine families are not proposed for VMs whose CPU is saturated.
• A Google Cloud Recommender recommendation replaces costerra's advice of the
  same kind for the same resource (rightsizing, idle resources, commitments).
• The potential savings total includes Google recommendations matched to the
  code (best option per resource).

Removed

• Rabbit (followrabbit.ai) integration: saved recommendations, the AI cost
  review (--rabbit-review, --rabbit-review-dry-run,
  COSTERRA_RABBIT_REVIEW) and .costerraignore. The rabbit_recommendations
  and rabbit_review keys of costerra.yml are now rejected as unknown keys:
  remove them.