OAuth 2: support scope_aliases in rabbitmq.conf

[MarcialRosales]

Is your feature request related to a problem? Please describe.

Users can configure almost all oauth2 settings via rabbitmq.conf using cuttlefish style configuration. However, there is still one setting called scope_aliases which is only supported in the erlang style.
This forces users to have two configuration files rabbitmq.conf and advanced.config. Furthermore, some users reported that it is harded for them to generate erlang style configuration using their templating engines (like Ansible).

Describe the solution you'd like

If the alias is just a single word like "admin" or "developer", the user can configure an scope alias like so

auth_oauth2.scope_aliases.admin = tag:administrator configure:*/*
auth_oauth2.scope_aliases.developer = tag:management configure:*/* read:*/* write:*/*

The scope is a space-separated list of strings.

However, if the alias has some symbols including the dot (.), the user can configure an scope alias like so:

auth_oauth2.scope_aliases.1.alias = api://administrator
auth_oauth2.scope_aliases.1.scope = tag:administrator configure:*/*
auth_oauth2.scope_aliases.2.alias = api://developer
auth_oauth2.scope_aliases.2.scope = tag:management configure:*/* read:*/* write:*/*