marshal nested secrets value to string

[iosmanthus]

This pull request marshals nested secret values according to the format of the secret file.

[iosmanthus]

Seem the serialized yaml value has some newline, I should trim the output string.

[Mic92]

So the idea is that we can have yaml and json encrypted without having to put them in strings? Would be nice to extend the test case those those as well: https://github.com/Mic92/sops-nix/blob/master/pkgs/sops-install-secrets/nixos-test.nix

The script to update secrets is here: https://github.com/Mic92/sops-nix/blob/master/pkgs/sops-install-secrets/test-assets/sops-edit

[iosmanthus]

So the idea is that we can have yaml and json encrypted without having to put them in strings? Would be nice to extend the test case those those as well: master/pkgs/sops-install-secrets/nixos-test.nix

The script to update secrets is here: master/pkgs/sops-install-secrets/test-assets/sops-edit

The basic idea is to support any value in a nested secret. However, I found some edge cases for this pull request:

1. It supports the value of the secret to be a number but shows as a string in the template rendering, I might add some type of information into the placeholder.
2. If the secret is a string formed by numbers, like "113", the rendered template would be like: ""123"".

I would add some tests to nixos-test.nix, and some unit tests for recurseSecretKey.

[Mic92]

Maybe it should only render arrays and hashmaps?