Warnings when FWF is used with ecto

[rewritten]

Hi :)

A bit related to #137 but it's probably independent from it.

When adding both FWF and Ecto as dependencies, the log starts being polluted with a lot of messages like

warning: Ecto.Changeset.cast/3 defined in application :ecto is used by the current 
application but the current application does not depend on :ecto. To fix this, you 
must do one of:
  1. If :ecto is part of Erlang/Elixir, you must include it under :extra_applications 
     inside "def application" in your mix.exs
  3. If :ecto is a dependency, make sure it is listed under "def deps" in your mix.exs
  4. In case you don't want to add a requirement to :ecto, you may optionally skip this 
     warning by adding [xref: [exclude: [Ecto.Changeset]]] to your "def project" in 
     mix.exs
  lib/fun_with_flags/store/persistent/ecto/record.ex:22: FunWithFlags.Store.Persistent.Ecto.Record.changeset/2

I'm not sure if this can be solved, but clearly FWF cannot depend on Ecto, but at the same time the app depends on ecto itself.

Maybe adding those ref excludes in FWF def project() would do?

I will attempt to use a local fork with these changes, but I'm not sure how we can actually test them in isolation.

[tompave]

Closing as it's possibly the same problem described in #137. We can reopen this if they turn out to be distinct.

[rewritten]

Indeed it's the same problem :)