When parsing the JSON response from the HTTP request to create a new certificate... Use `grep -Po` instead of `egrep` as egrep is not matching across all the lines we need to match.

Also trim leading whitespace from `token` by passing it through `tr`.

`rm` commands, if left unchecked can be dangerous, potentially destroying
unintended parts of the filesystem.

* Protect `rm` commands from empty variables with `${foo:?}` which will produce
  an error if `$foo` is unset or null.
* Create TEMP_DIR with `mktemp`.

Due to the call to create the destination directory
via 'mkdir -p "$(dirname "$to")"', the copy_file_to_location
function requires a filename and not the directory as a
destination.

Use copy_file_to_location as it appears to be intended and
check the exit status from the `cp' invocation for failures.