feat: make application changeset overridable

[StephaneRob]

Give the ability to override OauthApplication changeset/3. The main purpose is to add extra fields to an application without adding an new schema referencing it.

Example :

defmodule MyApp do
    @moduledoc false

    use Ecto.Schema

    use ExOauth2Provider.Applications.Application,
      otp_app: :ex_oauth2_provider

    schema "oauth_applications" do
      field(:description, :string)
      field(:reference, Ecto.UUID)

      application_fields()
      timestamps()
    end

    def changeset(application, params, config \\ []) do
      super(application, params, config)
      |> Ecto.Changeset.cast(params, [:reference, :description])
      # |> additional validations
    end
  end

NOTE: What do you think about running elixir formatter for all files in a specific commit? (#77)

[StephaneRob]

Actually not really necessary can be also done with the following code:

defmodule MyApp do
    @moduledoc false

    use Ecto.Schema

    use ExOauth2Provider.Applications.Application,
      otp_app: :ex_oauth2_provider

    alias ExOauth2Provider.Applications.Application

    schema "oauth_applications" do
      field(:description, :string)
      field(:reference, Ecto.UUID)

      application_fields()
      timestamps()
    end

    def changeset(application, params) do
      Application.changeset(application, params, otp_app: wh_api)
      |> Ecto.Changeset.cast(params, [:reference, :description])
      # |> additional validations
    end
end