Scannable map or struct assertions

[hauleth]

@marick

Consider code like this:

animal = AnimalT.update_for_success(original.id, params)
assert animal.name == "New Bossie"
assert animal.lock_version == 2

I find it easier to read something like that:

assert %{
    name: "New Bossie",
    lock_version: 2
  } = AnimalT.update_for_success(original.id, params)

This also makes “predicates” simpler:

assert %{
    name: "Bossy",
    tags: tags
  } = bossify("Bossy")
assert Enum.empty?(tags)