Checkpoints: Part 1 of Added docs

Signed-off-by: Marcin Woźniak <y0rune@aol.com>

buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java

@@ -12,6 +12,10 @@ public class ExchangeService {
     @Autowired
     private ExchangeRepository repo;
 
+    /** 
+     * @param exchange Instance to save in database
+     * @return Exchange Instance contains database id
+     */
     public Exchange save(Exchange exchange){
         return this.repo.save(exchange);
     }