json-schema-catalog-rs-formats: use more idiomatic formats.json instead of toFile/toJSON (#508997)

{

  json-schema-catalog-rs,

  runCommand,

  writeText,

  formats,

}:

let

  sample = builtins.toFile "example-schema.json" (

    builtins.toJSON {

  sample = (formats.json { }).generate "example-schema.json" {

    "$schema" = "http://json-schema.org/draft-07/schema#";

    "$id" = "https://example.com/example-2.9.json";

    "title" = "Example Schema";

    }

  );

  };

  expectedOutput = builtins.toFile "expected-output" ''

  expectedOutput = writeText "expected-output" ''

    {

      "groups": [

        {