fix: env refactor for Vite wrap-up [LIBS-690]

[KaiVandivier]

Part of LIBS-690

process.env vs. import.meta.env

Vite adds environment variables to the import.meta.env namespace by default. My plan was to make this the standard for the platform, too, because I thought this was a standard format that goes along with ES Modules. It turns out that it’s not standard, actually; it’s a pattern specific to Vite. Other build tools tend to use process.env as the default.

I've noticed that there are some other tools and packages out there that depend on configuration variables that are set on process.env, so dropping support for it entirely in favor of import.meta.env may be a bit weird.

This makes me think we should continue adding env vars to process.env, since it’s a little more generic, instead of migrating entirely to import.meta.env as the main env var namespace for the platform.

We can still deprecate the REACT_APP_-prefixed variable names, i.e. process.env.REACT_APP_DHIS2_APP_VERSION => process.env.DHIS2_APP_VERSION. We can handle it in the same way we planned to handle moving to import.meta.env i.e., have both variable names available in v12, then remove the REACT_APP_ versions in v13.

If we do, I’m not sure how much attention to give import.meta.env — Right now, Vite is configured to filter the env for values starting with “DHIS2_” and add them to import.meta.env. It seems that only values on import.meta.env can be used in HTML files, like %DHIS2_APP_NAME% in index.html. I propose we kinda keep import.meta.env as-is; some people may want to use it, and it doesn't really hurt to add the DHIS2_ prefixed env vars onto it.

Other env vars

I made some other changes to make the env var objects more concise:

1. Remove PWA default variables, and instead handle undefined values
2. Remove variables with undefined values from the env

I tested these out by starting and building both the simple-app and pwa-app examples to make sure they work with and without env vars. I also inspected the SW's caching behavior in the PWA app, and it looks good.

Examples

Before:

After: