This PR brings user invites logic to the Management service
via HTTP API.
The POST /users/ API endpoint creates a new user in the Idp
and then in the local storage.
Once the invited user signs ups, the account invitation is redeemed.
There are a few limitations.
This works only with an enabled IdP manager.
Users that already have a registered account can't be invited.
This PR is a part of an effort to use standard ports (443 or 80) that are usually allowed by default in most of the environments.
Right now Management Service runs the Let'sEncrypt manager on port 443, HTTP API server on port 33071,
and a gRPC server on port 33073. There are three separate listeners.
This PR combines these listeners into one.
With this change, the HTTP and gRPC server runs on either 443 with TLS or 80 without TLS
by default (no --port specified).
Let's Encrypt manager always runs on port 443 if enabled.
The backward compatibility server runs on port 33073 (with TLS or without).
HTTP port 33071 is obsolete and not used anymore.
Newly installed agents will connect to port 443 by default instead of port 33073 if not specified otherwise.
