Allow explicit type selection in hiera values

[oxc]

Allow specifying an explicit type instead of auto when specifying keys in hiera, e.g.

domain:
  example.com:
    path: /var/lib/rspamd/dkim/$domain.$selector.key
    'selector: string': 20200822

When this is possible, allow arrays to be printed as config-arrays:

    rates:
      some_limit:
        selector: 'user.lower'
        'bucket: array':
          - burst: 100
            rate: "10 / 1min"
          - burst: 10
            rate: "100 / 1min"

this should result in:

rates {
  some_limit {
    selector = "user.lower";
    bucket = [
    {
      burst = 100;
      rate = "10 / 1min";
    },
    {
      burst = 10;
      rate = "100 / 1min";
    }
    ]
  }
}

The exact syntax has still TBD, but I believe key: type should have the least potential for clashing with future keys/features, while being a common way to specify types in many langauges.

[oxc]

This would fix #6 and the selector use-case mentioned in #6 (comment)

[kienanstewart]

I think this would also help with the following use case: set a string value of YES in a configuration value. Since YES gets interpreted via the auto type as boolean, it's output without string quoting. Unless I'm mistaken, there's not a way to get the the output as a string without going through some hoops and creating rspamd::config resources in another way.