This is a required change because with dot case we cannot reference
other modules inside JSDoc `@type` annotations. For example, if you want
to reference `@type {./deploy.controller.FooType}` does not work,
because the compiler does not know whether `deploy` is a module or
`deploy.controller`. Changing dot case to undersocre, camel or dash case
solves this problem.

I decided to go with underscore case because this is what golang uses
(e.g., `foo_test.js`) so we'll have higher similarity of backend and
frontend codebases.