* authorize: authorization module adds support for per-route access policy. In this release we support the most common forms of identity based access policy: `allowed_users`, `allowed_groups`, and `allowed_domains`. In future versions, the authorization module will also support context and device based authorization policy and decisions. See website documentation for more details.
* docs: updated `env.example` to include a `POLICY` setting example.
* docs: added `IDP_SERVICE_ACCOUNT` to `env.example` .
* docs: removed `PROXY_ROOT_DOMAIN` settings which has been replaced by `POLICY`.
* all: removed `ALLOWED_DOMAINS` settings which has been replaced by `POLICY`. Authorization is now handled by the authorization service and is defined in the policy configuration files.
* proxy: `ROUTES` settings which has been replaced by `POLICY`.
* internal/log: `http.Server` and `httputil.NewSingleHostReverseProxy` now uses pomerium's logging package instead of the standard library's built in one.
Closes#54Closes#41Closes#61Closes#58
