bug: Accept either paths or strings containing the cert for APNS

[jrconlin]

Closes #240

Description

Allow APNS certificates to be inlined into environment variables.

NOTE
The Environment Variable name needs to be specified as:

AUTOEND_APNS__CHANNELS (note the double underscore between APNS and CHANNELS.)

inlined certificates should include new line characters (e.g.
AUTOEND_APNS__CHANNELS='{"dev":{"cert":"-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----","key": "-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----"}}'

Values that do not begin with a "-" are presumed to be paths to key and certificates.

Testing

While this will not produce a valid APNS key, you can generate a readable PKCS8 cert and key file using the following:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365
openssl pkcs8 -topk8 -inform pem -outform pem -in key.pem -out pkcs8.key -nocrypt

cert.pem = the cert value
pkcs8.key = the key value

These can be incorporated into a bash command to verify that the APNS service is started.

Issue

Closes #240

[jrconlin]

@Mcat12, yes. Under bash (and a few other shells) "." will break an environment variable, which will cause things to fail.

[fzzzy]

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