- Implement ActorKeyEndpoint, ActorKeysEndpoint.
- Implement user, client keys in `ActorEndpoint#delete`, `#put`.

- RestBase
  - Fix RestErrorResponse exceptions to report actual `rest_path`
    instead associated with the failed data store operation instead of
    `request.rest_path`.
  - Move `json_response`, `already_json_response` args `request_version`
    and `response_version` into options hash; add docs.

- DataError, RestErrorResponse: Pass useful message text to `super`.

- RestRouter: Clean up logging
  - Print request methods, paths and bodies more readably for log_level >= INFO.
  - Pretty-print RestRequest objects (only printed when log_level == DEBUG).

- Server: Change default log_level to `:warn` (to enable logging cleanup above).

- `Rakefile`, `spec/run_oc_pedant.rb`
  - Consume RSpec, Pedant options from `ENV['RSPEC_OPTS']`, `ENV['PEDANT_OPTS']` (see `rake -D`).
  - Consume `ENV['LOG_LEVEL'` (see `rake -D`).
  - Clean up ChefZero::Server default opts and move duplicated logic to `start_chef_server` method.

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