refactor(AddParticipantDbDto): include all members into toString() method.

I couldn't remember why I decided to exclude some members in
655ff33 commit but at this moment I
feel that logggig all members is useful for debugging.

[skip ci]

Author: php-coder

src/main/java/ru/mystamps/web/feature/participant/AddParticipantDbDto.java

@@ -23,7 +23,7 @@
 
 @Getter
 @Setter
-@ToString(of = { "name", "buyer", "seller" })
+@ToString
 public class AddParticipantDbDto {
 	private String name;
 	private String url;