Handle environment variables

[robbiemccorkell]

Adding react-native-config to allow for the use of a .env file to pass environment variables.

There's a few options out there which do similar things. Once example is react-native-dotenv which simply inlines the environment variables using babel, but I couldn't get it, or similar projects to work.

It seems like it's pretty much impossible to hide secrets from app bundles so the right way to do it is to call back to a server which handles any API key you are using. However I can't really see how that doesn't just make the problem worse because then you're opening up a public API anyone could use.

Either way, I think the variables we will be using aren't hugely sensitive. At least initially we will only be using the read-only contentful API key, which doesn't particularly matter if it leaks, and can be revoked if it starts to get spammed.

Anyone have thoughts?

Pre-flight check-list

Before raising a pull request

• Documentation
• Unit tests
• Build passing

Pre-merge check-list

• Code review (At least one 👍)
• Tester approved

[robbiemccorkell]

It looks like react-native-config reads .env files, but doesn't read environment variables at build time (why would it I guess). This PR now includes a short script to read vars listed in .env.example, collect the appropriate env vars from process.env and generate a .env file. This file is then persisted to the native build steps.

Ready for review.

[markholland]

Good to get this figured out, works as expected

[robbiemccorkell]

Awesome thanks @markholland