Closes #6: Implemented a "source" attribute for tracks.

app/Http/Controllers/Api/V1/TracksController.php

@@ -100,7 +100,11 @@ class TracksController extends \ApiControllerBase
                 'small' => $track->getCoverUrl(Image::SMALL),
                 'normal' => $track->getCoverUrl(Image::NORMAL)
             ],
-            'comments' => $comments
+            'comments' => $comments,
+
+            // As of 2015-10-28, this should be expected to produce either
+            // "direct_upload" or "mlpma" for all tracks.
+            'source' => $track->source
         ], 200);
     }
 }

database/migrations/2015_10_26_231224_AddTrackSourceColumn.php

@@ -0,0 +1,39 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class AddTrackSourceColumn extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('tracks', function(Blueprint $table){
+            $table->string('source', 40)->default('direct_upload');
+        });
+
+        // Mark MLPMA tracks retroactively
+        // --> The default value in the database, set above, will
+        //     be used automatically for all non-MLPMA tracks.
+        $tracks = DB::table('tracks')
+            ->join('mlpma_tracks', 'mlpma_tracks.track_id', '=', 'tracks.id');
+
+        $tracks->whereNotNull('mlpma_tracks.id')->update(['source' => 'mlpma']);
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('tracks', function(Blueprint $table){
+            $table->dropColumn('source');
+        });
+    }
+}