Add an optional "content" parameter to the freeradius::cert resource.
This allows the user to pass in raw content rather than just
a direct file resource. Great for use cases where people don't
store private keys in raw files in their repo, but use some alternative
method to get them.
Set file permissions on the installed certificate differently depending on whether this is a private key or a public certificate. Note that the default is to treat the file as a private key and remove world-readable privileges. Allowable values: `cert`, `key`. Default: `key`.