- schow no contributor in oai if no contributor is defined

- add contributor_type during creating the dataset

database/migrations/2020_04_27_124302_add_contributor_type_to_documents_persons.php

@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Support\Facades\Config;
+
+class AddContributorTypeToDocumentsPersons extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('link_documents_persons', function (Blueprint $table) {
+            $table->enum('contributor_type', Config::get('enums.contributor_types'))->nullable();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('link_documents_persons', function (Blueprint $table) {
+            $table->dropColumn('contributor_type');
+        });
+    }
+}