add functions for Repo to accept DgraphEx.Changesets

[elbow-jason]

It would be nice to be able to pipe a changeset directly into repo and decide in the repo whether to send or reject the changes.

[elbow-jason]

This would also remove the need for Changeset.uncast to be included in the changeset function of a model.

[elbow-jason]

also this would keep confusing down about which models have been through changesets and saved already vs models that have simple been uncast.

[elbow-jason]

added to Repo.insert and Repo.update by commit c0bafe8

  test "Repo.insert returns error tuple given an invalid changeset" do
    changes = %{}
    {:error, %Changeset{} = changeset} =
      %Company{}
      |> Company.changeset(changes)
      |> Repo.insert
    assert changeset.errors == [name: :invalid_string, name: :cannot_be_nil]
  end

  test "Repo.insert returns an inserted model if everything is ok" do
    changes = %{name: "Wot"}
    company =
      %Company{}
      |> Company.changeset(changes)
      |> Repo.insert
    assert company.__struct__ == Company
    assert company.name == "Wot"
    assert company._uid_ |> is_binary
  end

  test "Repo.update returns an error tuple for invalid changes" do
    company1 = Repo.insert(%Company{
      name: "Flim",
    })
    changes = %{name: 1}
    {:error, %Changeset{} = changeset} =
      company1
      |> Company.changeset(changes)
      |> Repo.update
    assert changeset.errors == [name: :invalid_string]
  end

  test "Repo.update returns an inserted model for valid changes" do
    company1 = Repo.insert(%Company{
      name: "Flim",
    })
    changes = %{name: "Beefer"}
    company2 =
      company1
      |> Company.changeset(changes)
      |> Repo.update

    assert company2._uid_ == company1._uid_
    assert company2.name == "Beefer"
    company3 = Repo.get(Company, company1._uid_)
    assert company2 == company3
  end