Add query to extract JSON Film data

Author: michael-simons

src/misc/select_films_as_json.sql

@@ -0,0 +1,15 @@
+select row_to_json(r) 
+  from (
+    select 'de.springbootbuch.mongo.Film' as _class,
+           title, 
+           release_year as releaseYear,
+           (select array_to_json(array_agg(row_to_json(a))) 
+              from (
+                select first_name as firstName, last_name as lastName
+                  from film_actor fa 
+                  join actor ac using (actor_id) 
+                 where fa.film_id = f.film_id
+              ) a
+           ) as actors
+      from film f
+) r;