endpoint: Read APN certs from environment

[oremj]

Can we read APN certs from the APNS.CHANNELS environment variable instead of looking for files?

Example of what I have now in dev:

{
  "dev": {
    "cert": "-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----\n",
    "key": "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----\n"
  },
  "stage": {
    "cert": "-----BEGIN CERTIFICATE-----\n...\n",
    "key": "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----\n"
  }
}

[oremj]

I assume this would involve modifying

autopush-rs/autoendpoint/src/routers/apns/router.rs

Lines 85 to 86 in 0f168c9

	let cert = tokio::fs::read(settings.cert).await?;
	let key = tokio::fs::read(settings.key).await?;

and

autopush-rs/autoendpoint/src/routers/apns/settings.rs

Lines 21 to 22 in 0f168c9

	pub cert: PathBuf,
	pub key: PathBuf,

[jrconlin]

hrm.

so rust's serde::deserializer is pretty clear that it's not a parsing library, and will panic if it encounters a control character inside of a string. Simply replacing newlines with a space would get us past the (lack of) parser.

In addition, we'll probably have to rename the ENV to something like AUTOEND_APNS__CHANNELS

I'm working on trying to get something running locally.