team.ex

defmodule Web.Team do
  use Web.Web, :model

  schema "teams" do
    field :name, :string
    many_to_many :users, join_through: 'team_members', on_delete: :delete_all
    timestamps()
  end

  @doc """
  Builds a changeset based on the `struct` and `params`.
  """
  def changeset(struct, params \\ %{}) do
    struct
    |> cast(params, [:name])
    |> validate_required([:name])
  end
end

team_member.ex

defmodule Web.TeamMember do
  use Web.Web, :model


  schema "team_members" do
    has_one :user, User
    has_one :team, Team
    timestamps()
  end

  @doc """
  Builds a changeset based on the `struct` and `params`.
  """
  def changeset(struct, params \\ %{}) do
    struct
    |> cast(params, [:user_id, :team_id])
    |> validate_required([:user_id, :team_id])
  end
end

user.ex

defmodule Web.User do
  use Web.Web, :model
  use Coherence.Schema

  schema "users" do
    field :name, :string
    field :email, :string
    coherence_schema
    many_to_many :teams, Web.Team, join_through: 'team_members'
    timestamps
  end

  def changeset(model, params \\ %{}) do
    model
    |> cast(params, [:name, :email] ++ coherence_fields)
    |> validate_required([:name, :email])
    |> unique_constraint(:email)
    |> validate_coherence(params)
  end
end