Clarify documentation for @Modifying.

Modifying queries are executed directly against the database.
No events or callbacks get called.
Therefore also fields with auditing annotations do not get updated if they don't get updated in the annotated query.

Closes #970

Author: schauder

spring-data-r2dbc/src/main/asciidoc/reference/r2dbc-repositories.adoc

@@ -253,6 +253,10 @@ The result of a modifying query can be:
 The `@Modifying` annotation is only relevant in combination with the `@Query` annotation.
 Derived custom methods do not require this annotation.
 
+Modifying queries are executed directly against the database.
+No events or callbacks get called.
+Therefore also fields with auditing annotations do not get updated if they don't get updated in the annotated query.
+
 Alternatively, you can add custom modifying behavior by using the facilities described in <<repositories.custom-implementations,Custom Implementations for Spring Data Repositories>>.
 
 [[r2dbc.repositories.queries.spel]]

src/main/asciidoc/jdbc.adoc

@@ -700,6 +700,10 @@ You can specify the following return types:
 * `int` (updated record count)
 * `boolean`(whether a record was updated)
 
+Modifying queries are executed directly against the database.
+No events or callbacks get called.
+Therefore also fields with auditing annotations do not get updated if they don't get updated in the annotated query.
+
 include::{spring-data-commons-docs}/query-by-example.adoc[leveloffset=+1]
 include::query-by-example.adoc[leveloffset=+1]