allow mongocli read configs from stdin rather than from file
To deploy new cluster we need prepare config file and put there all sensitive data, like automation user password, ssl cert passwords etc.
Then we have to specify -f flag to point to this config during mongocli call.
Currently this file has to persist somewhere on the disk during call to CLI which makes it insecure (and file has to be carefully removed after cli call finished, proper access to the file has to be set etc)
It would be safer to send this config to stdin of mongocli - as a pipe from another command which can generate the whole config in memory without persisting on disk.