Add recovery fallback for secrets.json file

Sometimes the `secrets.json` is either deleted (accidentally) or corrupted. Instead of this, @tyeth and I were discussing a way to store, on boot, the `secrets.json`'s content in-memory and persist it through boot cycles.

On boot, the device would:
1) check for the existence of this content, recover it and place into a new secrets.json file on the FS
2) create a new `secrets.json` file (current operation)

We'd need to:
* Profile the secret.json max. possible size
* Consider using a struct or just a string depending on serialization/deserialization difficulty.

Start by locating the boot-time handling for secrets.json and the filesystem operations that create it. Profile the file's maximum size, then evaluate whether an in-memory struct or string can be serialized and restored; done means a missing or corrupted secrets.json is recovered across boot cycles.

Written by the indexing model from the issue text.