v0.6.0

0.6.0

• Breaking: the central-auth-platform defines are renamed
  CENTRAL_PROJECT_ID and CENTRAL_FUNCTIONS_BASE_URL (from
  SPECTRUM_CENTRAL_PROJECT_ID / SPECTRUM_CENTRAL_FUNCTIONS_BASE_URL), and
  centralProjectId no longer defaults to Spectrum's own Firebase project.
  This package has no built-in central project now: CentralRestAuthClient
  throws ArgumentError at construction if CENTRAL_PROJECT_ID is unset and
  no centralFunctionsBaseUrl was passed explicitly, instead of silently
  resolving to spectrumtasks-81c63. An app depending on the old default
  passes --dart-define=CENTRAL_PROJECT_ID=<its central project> (or
  centralFunctionsBaseUrl directly) going forward.
• Doc comments and the README no longer name Spectrum specifically; the
  central-auth-platform handshake is a general pattern, not tied to one team.