to_existing_atom blows up when loading new values from DB

[kenips]

Not sure the rationale behind using to_existing_atom on load, but I guess the idea is that you're not trusting the database? If we input a new string value in the DB the current load function would blow up as the atom doesn't exist.

[janpieper]

Warning: this function creates atoms dynamically and atoms are not garbage-collected. Therefore, string should not be an untrusted value, such as input received from a socket or during a web request. Consider using to_existing_atom/1 instead.

See https://hexdocs.pm/elixir/String.html#to_atom/1

[voughtdq]

I created a version using the new Ecto.ParameterizedType behaviour that does what you're asking:

https://gist.github.com/voughtdq/a4930fd9c8ce10f2899a3476e94aba1a