Use APP_ID instead of the non-existing APP_NAME

[eyalch]

Looks like the action is referencing a non-existing app-wide variable named APP_NAME.

Reading the app-wide variables section in the docs, the available app-wide variables are:

• APP_DOMAIN
• APP_URL
• APP_ID

Since the action correctly references APP_DOMAIN and APP_URL, and since there's no reference to APP_NAME anywhere in the docs, I'm assuming a typo resulted in APP_NAME instead of APP_ID.

In addition to the fix, I added a test that makes sure that all the supported app-wide variables are handled correctly.

[markusthoemmes]

Nice catch! Thanks a lot!

Let me know if you want to adjust the test as proposed. If not, we can merge as-is as well.

[markusthoemmes]

This is part of v2.0.5. Thanks for the contribution @eyalch!