keyFilename and env variables

[JFGHT]

Basically I'm having a similar problem to this one: googleapis/google-cloud-node#136

and I didn't find in the docs any other approach than the keyFilename which it only accepts a string to the path of the file.

[leeuwd]

Check #91

[schmidt-sebastian]

The issue pointed to by @leeuwd contains a sample for how to do this. I will add this to our JSDoc to make this obvious.

[leeuwd]

For future reference and/or help others: if you use the credentials: {...} object to initialize Firestore and retrieve the client_email and private_key values from the Firebase environment configuration (e.g. values set with firebase functions:config:set someservice.key="THE API KEY"), you have to fix line endings:

functions.config().private_key

becomes

functions.config().private_key.replace(/\\n/g, '\n'),

Otherwise, you'll get Firebase cloud function errors like "routines:PEM_read_bio:no start line".