setting micronaut configuration location

I have an existing groovy micronaut app I'm trying to change where it loads its config from. I don't understand what code to write so I can set the location of the micronaut configuration. I know you can use micronaut.config.files system variable or MICRONAUT_CONFIG_FILES environment variable, but this is a terrible idea because micronaut is built into grails and therefore every grails app you have running in tomcat will pick up the same config and crash.

Nor do I know where in the code to set the config file. There's an Application class with a run() method, but I don't know if this is only called during development, or whether it gets called when deploying in Tomcat. When setting the config in a Grails app, there is an Application class extending EnvironmentAware, and you can override setEnvironment, and load external configs there, but there is no hint of that for micronaut apps.

The micronaut doco says it can load a configuration from "application.{extension}", but it doesn't say what "application" is, or what directory it expects that in, or whether you can change the directory. Is "application" the value of micronaut.application.name in one's application.yml? I couldn't seem to get it to load based on that.

Then the documentation talks about loading from a PropertySource, which is fine and all, but doesn't tell you where you can put that code to load from a PropertySource. There is mention you can pass the PropertySource to ApplicationContext.run(xx), but in this app I inherited, there is no mention of ApplicationContext, and the micronaut documentation isn't very clear what I'm supposed to do with ApplicationContext. This app I've inherited has an Application class with a main() calling Micronaut.run() which apparently returns an ApplicationContext, but it's not clear if main() is called when running in Tomcat, or whether I should be calling run() on that, when it works as is, and I'm just trying to change where it loads its config.