[Enhancement] Improve ordering of models (#164)

* [WIP] ordering app queries

* Refactored media queries to be self-contained

lib/pinchflat/sources/sources_query.ex

@@ -0,0 +1,31 @@
+defmodule Pinchflat.Sources.SourcesQuery do
+  @moduledoc """
+  Query helpers for the Sources context.
+
+  These methods are made to be one-ish liners used
+  to compose queries. Each method should strive to do
+  _one_ thing. These don't need to be tested as
+  they are just building blocks for other functionality
+  which, itself, will be tested.
+  """
+  import Ecto.Query, warn: false
+
+  alias Pinchflat.Sources.Source
+
+  # Prefixes:
+  # - for_* - belonging to a certain record
+  # - join_* - for joining on a certain record
+  # - with_* - for filtering based on full, concrete attributes
+  # - matching_* - for filtering based on partial attributes (e.g. LIKE, regex, full-text search)
+  #
+  # Suffixes:
+  # - _for - the arg passed is an association record
+
+  def new do
+    Source
+  end
+
+  def for_media_profile(query, media_profile) do
+    where(query, [s], s.media_profile_id == ^media_profile.id)
+  end
+end