Dotenv's variable substitution doesn't work the same way as commands run
in the shell. It needs values to be escaped.
```sh
$ cat /tmp/env
SECRETS=$(cat /tmp/json)
SECRETS2=$(echo $SECRETS | jq)
$ cat /tmp/json
\{\ \"foo\"\ :\ \"bar\" \}
$ SECRETS=$(cat /tmp/json)
$ SECRETS2=$(echo $SECRETS | jq)
jq: parse error: Invalid numeric literal at line 1, column 2
$ ruby -e 'require "dotenv"; puts Dotenv.parse("/tmp/env")["SECRETS2"]'
{
"foo": "bar"
}
```
Since you then can't use the shell to debug, `kamal secrets print` will
allow you to see what the secrets will be set to.
