* master: (42 commits)
  build: Switch to vendored openssl build (#914)
  feat(server): Add inbound filters functionality to dynamic sampling (#920)
  fix rule generation to new format (in tests) (#939)
  ref: Remove actix-web client, make reqwest the new http client (#938)
  fix(server): Reject empty envelopes with an explicit error (#937)
  fix(server): Ensure outcome data categories are numeric (#936)
  feat(stats): Add data category to TrackOutcome (#931)
  fix(pii): Make username pii-strippable (#935)
  build: Bump symbolic to 8.0.4 (#899)
  fix: Update to tokio 1.0 (#909)
  fix(pii): Make and/or work correctly with pii=maybe (#932)
  release: 21.2.0
  release: 0.8.3
  fix(build): Fix path to 3.7 (#930)
  build: drop python 2.7 support (#929)
  feat(protocol): Add snapshot to the stack trace interface (#927)
  test: Improve integration tests to reduce flakyness (#928)
  fix: Ignore false-positive lints from Clippy 1.50 (#926)
  feat(protocol): Add NSError to mechanism (#925)
  meta: Fix changelog
  ...