- 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

app/Library/Xml/DatasetExtension.php

@@ -78,6 +78,7 @@ trait DatasetExtension
         ),
         'Subject' => array(
             'model' => Subject::class,
+            'through' => 'link_dataset_subjects',
             'relation' => 'subjects',
             'fetch' => 'eager'
         ),