Relax ScrobbleRule.t to allow unpersisted structs

lib/music_library/scrobble_rules.ex

@@ -49,7 +49,7 @@ defmodule MusicLibrary.ScrobbleRules do
   def get_scrobble_rule!(id), do: Repo.get!(ScrobbleRule, id)
 
   @spec create_scrobble_rule(map()) :: {:ok, ScrobbleRule.t()} | {:error, Ecto.Changeset.t()}
-  def create_scrobble_rule(attrs \\ %{}) do
+  def create_scrobble_rule(attrs) do
     %ScrobbleRule{}
     |> ScrobbleRule.changeset(attrs)
     |> Repo.insert()

lib/music_library/scrobble_rules/scrobble_rule.ex

@@ -5,9 +5,9 @@ defmodule MusicLibrary.ScrobbleRules.ScrobbleRule do
 
   @type t :: %__MODULE__{
           id: integer() | nil,
-          type: :album | :artist,
-          match_value: String.t(),
-          target_musicbrainz_id: String.t(),
+          type: :album | :artist | nil,
+          match_value: String.t() | nil,
+          target_musicbrainz_id: String.t() | nil,
           enabled: boolean(),
           description: String.t() | nil,
           inserted_at: DateTime.t() | nil,