Fix #235: use Option instead of direct nulls in the quote API

Author: ForNeVeR

scala/src/main/scala/ru/org/codingteam/loglist/dto/QuoteDTO.scala

@@ -1,3 +1,3 @@
 package ru.org.codingteam.loglist.dto
 
-case class QuoteDTO(id: Long, source: String, sourceUrl: String, time: Long, content: String, rating: Int)
+case class QuoteDTO(id: Long, source: String, sourceUrl: Option[String], time: Long, content: String, rating: Int)

scalajvm/app/controllers/api/Quotes.scala

@@ -50,7 +50,7 @@ class Quotes @Inject()(implicit cc: ControllerComponents, configuration: Configu
     }
 
   private def buildQuoteDto(quote: Quote): QuoteDTO =
-    QuoteDTO(quote.id, quote.source, quote.sourceUrl.orNull, quote.time.toInstant.toEpochMilli, quote.content.getOrElse(""), quote.rating)
+    QuoteDTO(quote.id, quote.source, quote.sourceUrl, quote.time.toInstant.toEpochMilli, quote.content.getOrElse(""), quote.rating)
 
   private def json(text: String) = Ok(text).as("application/json; charset=utf-8")
 }