Reorder documentation of class-based projection support for JPA Nativ…

…e Queries.

Closes spring-projects#3599

src/main/antora/modules/ROOT/pages/repositories/projections.adoc

@@ -1,9 +1,17 @@
 [[jpa.projections]]
 = Projections
 
-include::{commons}@data-commons::page$repositories/projections.adoc[leveloffset=+1]
+:projection-collection: Collection
+
+include::{commons}@data-commons::page$repositories/projections-intro.adoc[]
 
 NOTE: It is important to note that <<projections.dtos,Class-based projections>> with JPQL is limited to *constructor expressions* in your JPQL expression, e.g. `SELECT new com.example.NamesOnly(u.firstname, u.lastname) from User u`.
 (Note the usage of a FQDN for the DTO type!) This JPQL expression can be used in `@Query` annotations as well where you define any named queries.
 And it's important to point out that class-based projections do not work with native queries AT ALL.
 As a workaround you may use named queries with `ResultSetMapping` or the Hibernate-specific javadoc:{hibernatejavadocurl}org.hibernate.query.ResultListTransformer[]
+
+include::{commons}@data-commons::page$repositories/projections-interface.adoc[leveloffset=1]
+
+include::{commons}@data-commons::page$repositories/projections-class.adoc[leveloffset=1]
+
+