Unable to use custom list inside enabled_plugins file

[enothen]

The current template templates/enabled_plugins.erb allows a static list of plugins to be enabled, and nothing else outside of what the template covers:

% This file managed by Puppet
% Template Path: <%= @module_name %>/templates/enabled_plugins
<%- @_plugins = [] -%>
<%- if @admin_enable or @management_enable -%>
  <%- @_plugins << 'rabbitmq_management' -%>
<%- end -%>
<%- if @stomp_ensure -%>
  <%- @_plugins << 'rabbitmq_stomp' -%>
<%- end -%>
<%- if @ldap_auth -%>
  <%- @_plugins << 'rabbitmq_auth_backend_ldap' -%>
<%- end -%>
<%- if @config_shovel -%>
  <%- @_plugins << 'rabbitmq_shovel' -%>
  <%- if @admin_enable or @management_enable -%>
    <%- @_plugins << 'rabbitmq_shovel_management' -%>
  <%- end -%>
<%- end -%>
[<%= @_plugins.join(',')%>].

There's no way to enable rabbitmq_prometheus, or any other plugin when using rabbitmq::use_config_file_for_plugins: True.

[wyardley]

Closed via #917