[Housekeeping] Refactor settings model (#165)

* [WIP] renamed current settings module and tables to have backup suffix

* Created new settings table, schema, and context

* Migrated from old settings module to new one

* Removed settings backup modules

* Added some tests and docs

test/pinchflat_web/controllers/page_controller_test.exs

@@ -10,7 +10,7 @@ defmodule PinchflatWeb.PageControllerTest do
     end
 
     test "displays the onboarding page when onboarding is forced", %{conn: conn} do
-      Settings.set!(:onboarding, false)
+      Settings.set(onboarding: false)
 
       conn = get(conn, ~p"/?onboarding=1")
       assert html_response(conn, 200) =~ "Welcome to Pinchflat"
@@ -25,7 +25,7 @@ defmodule PinchflatWeb.PageControllerTest do
     end
 
     test "displays the home page when not onboarding", %{conn: conn} do
-      Settings.set!(:onboarding, false)
+      Settings.set(onboarding: false)
 
       conn = get(conn, ~p"/")
       assert html_response(conn, 200) =~ "MENU"