Basic Enable/Disable for Plugins

[jmbrunskill]

Is your feature request related to a problem? Please describe

It would be good to be able to deploy the notify server with only specific plugins available, particulary if you want to build a custom plugin for example.

This would be a stop gap measure until we have a proper plugin system, rather than compiling all the plugins as part of the main configuration.

Describe the solution you'd like

A list of enabled plugins in the configuration file?

Acceptance Criteria

• Something

Describe alternatives you've considered

Each plugin could have it's own custom settings potentially, which would mean the local.yaml could be extended, or maybe there's a coldchain.yaml file for coldchain plugin?

Additional context