Secrets Mechanism

[jleandroperez]

Description:

This PR implements a (hopefully cute) mechanism which will allow us to locally store all of the App "Secrets" (API Keys and so on), and prevent exposing them to GH.

This mechanism mirrors what we've got for WPiOS, with a slight difference: we're performing a replacement OP over placeholders (while WPiOS actually generates the ApiCredentials file, entirely in Swift).

Details:

1. Secrets are to be stored at ~/.woo_app_credentials.json)
2. Credentials "Template" at Credentials/ApiCredentials.swift. This file is not part of any target, and never gets built directly.
3. New Build Phase, in charge of running replace_credentials.rb
4. This cute script will perform replacement OP's over the Template
5. Generated file is stored at /tmp/WooCommerce.build/ApiCredentials.swift
6. The project loads the generated file (at the absolute path)

Testing:

1. Try to build the app (without ~/.woo_app_credentials.json. Verify you get a build error
2. Install ~/.woo_app_credentials.json. Verify everything turns green!
3. Delete any entry in the credentials.json file. Verify you get an error.

Aaron, what do you think?. I've got the same process in bash, but i've learnt using eval is a really bad idea. Ruby feels swifty!

cc @mindgraffiti @astralbodies

[houndci-bot]

Trailing Whitespace Violation: Lines should not have trailing whitespace. (trailing_whitespace)

[mindgraffiti]

I know nothing about shell scripts D: but the tests all check out! It fails to build when the secrets file does not exist. It builds when secrets exist. It fails to build when a field has been omitted. (Command /bin/sh failed with exit code 1)

[jleandroperez]

On purpose 😄. The idea is for this to break... if there's a missing secret, so that we notice and don't ship with missing keys.

Thanks Thuy!!!