- change relation between document and dataset_subjects to M : n:

a. during creating a dataste, also find existing keywords and attach them
b. DatasetExtension.php
c. Subject.php: protected $table = 'dataset_subjects';
d. migration file for crete_dataset_subjects_table
- change api routes for also using url alias if defined
- composer updates: composer.lock

database/migrations/2021_06_07_135923_create_dataset_subjects_table.php

@@ -0,0 +1,58 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateDatasetSubjects extends Migration
+{
+    // php artisan make:migration create_dataset_subjects_table --table=dataset_subjects --create=dataset_subjects
+// php artisan migrate
+
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('dataset_subjects', function (Blueprint $table) {
+            $table->id();
+            $table->string('language', 3)->nullable();
+            $table->enum(
+                'type',
+                ['uncontrolled']
+            );
+            $table->string('value', 255);
+            $table->string('external_key', 255)->nullable();
+            $table->nullableTimestamps();
+        });
+
+        Schema::create('link_dataset_subjects', function (Blueprint $table) {
+            // $table->increments('id');
+
+            $table->unsignedInteger('subject_id')->index();
+            $table->foreign('subject_id')
+                ->references('id')->on('dataset_subjects')
+                ->onDelete('no action')->onUpdate('no action'); //detach the relation via code
+
+            $table->unsignedInteger('document_id')->index();
+            $table->foreign('document_id')
+                ->references('id')->on('documents')
+                ->onDelete('cascade')->onUpdate('cascade');
+
+            $table->primary(['subject_id', 'document_id']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('link_dataset_subjects');
+        Schema::dropIfExists('dataset_subjects');
+    }
+}