add support for templates in dict

[mgu]

Currently the "template" feature of vault-cli only works when the value is a string ({"value": "!template!..."}

We would like to also support templates when values are dict. For example:

{
  "value": {
    "a": "!template!...",
    "b": "!template!...",
    "c": "value",
  }
}

[ewjoachim]

Whoops, targetted the wrong ticket in the commits above.