The parser for the value read from a config.

It is designed to simplify reading and instantiating values read from json to elixir entities.

Supported types:

• {"type": "atom", "value": "foo"} — the atom :foo
• {"type": "existing_atom", "value": "foo"} — the existing atom :foo
• {"type": "function", "module": module, "function": function, "arity": arity} — the function to instantiate
• {"type": "existing_function", "module": module, "function": function, "arity": arity} — the existing function to instantiate
• {"type": "tuple", "value": ["foo", 42]} — the tuple {"foo", 42}