Context:
I'm building a recipe website with Angular frontend and Node.js express backend. I'm using Heroku for the backend and trying to use Firebase for the frontend. The backend is not ready for use, and is unstable. The frontend is almost ready for v1. For now, all I have is the ability to retrieve a list of recipes from the GET /api/recipes endpoint, and display them (and search through the loaded recipes). Eventually, I plan to add the ability to add/edit/delete/search through the recipes, as well as other endpoints. For now, it works equally well with a static .json file or a dynamic GET endpoint.
In the process of adding this to the backend, the backend will naturally go down and may become temporarily unusable at times, so I'm of course going to have two deployments of the API, and two deployments of the frontend. Prod and Dev, Live and Preview. This should be easy with Heroku, but Firebase is giving me some problems.
I want to have different configs for different deployments. A way for the front-end to ask Firebase "Where's the API I'm supposed to use". This shouldn't go in the repository, code once deploy many, yada: https://12factor.net/codebase . But I haven't figured out how to do this with Firebase.
Goal:
Firebase Remote Config should use a condition such as App Channel to send a different api_url parameter based on what channel the deployment is. This should not be stored in the repository. It should not give away the other deployments etc.
Whatever config I use should be build-once deploy-many. I do not wish to pass a config parameter such as configs:{"recipes.web.app":{apiUrl:"..."}, "recipes-preview-1239j20.web.app":{apiUrl:"..."}}. The frontend must not be aware of other deployments. It shouldn't even really have to be aware of where it's being hosted.
Current Progress:
I successfully deployed different versions to the live channel and the preview channel. I successfully made a RemoteConfig config using GUI (https://console.firebase.google.com/project/<project_name>/config). I did see how to add conditions. I successfully accessed RemoteConfig inside my custom service in Angular. I did find out that init.json on the preview and live channels are identical. I did successfully limit it to "If it's the recipe app", but it's useless because everything's the recipe app. There is a way to make multiple sites, but that's not really useful either, because I'd have to set up the entire app again.
I did not manage to figure out how to deploy remoteconfig.template.json from command line. I did not manage to figure out what conditions are useful. I did not manage to get the "Version" condition to be enabled in the condition selector. I did not manage to find any condition about "channels". I did not manage to find anything with "remote config" and "channels" even on the same page! I did not manage to find anything in firebase docs about "deployments".
Alternative and Unrelated Sidenote:
I'm extremely frustrated with Firebase, and if I can't figure this out, I'm going to abandon it in favor of a Heroku thing I just found. An "unsupported" buildpack for nginx (https://elements.heroku.com/buildpacks/heroku/heroku-buildpack-nginx). "Unsupported" as in it's unofficial. I'm familiar with nginx, and using that will make everything about this personal project (except the server location and build/deploy process) match up with what I'm doing at work. And also both halves of my personal project (static web and api) will be on the same host, which might make things nice.