Support derived queries on repositories defined with an abstract entity class. (#1366)

Motivation:
Currently an abstract entity class specified in the repository definition can
be used for the predicate typeKey = typeAlias(of abstract entity class) in
queries. Since documents are stored with typeKey = typeAlias(of concrete class)
those queries will never match any documents.  To allow this to work,
all of the abstract entity class an all concrete subclasses must use the
same typeAlias.

Once those documents are found, regardless of their concrete class,
they will all have the same typeKey = typeAlias, instead of having the
typeAlias specific to the concrete class. Additional information in
the stored document is needed to identify the concrete class (subtype
in the example test case), as well as a TypeMapper to interpret that
 information.

Changes:
This allows a common TypeAlias to be used for the purpose of the predicate
typeKey = typeAlias, and the determination of the concrete type by
implementing an AbstractingMappingCouchbaseConverter that inspects the
'subtype' property.

Closes #1365.

Co-authored-by: Michael Reiche <[email protected]>

Author: mikereiche

src/test/java/org/springframework/data/couchbase/domain/User.java

@@ -30,6 +30,17 @@
 import org.springframework.data.couchbase.core.mapping.Document;
 
 import java.io.Serializable;
+import java.util.Objects;
+
+import org.springframework.data.annotation.CreatedBy;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.annotation.LastModifiedBy;
+import org.springframework.data.annotation.LastModifiedDate;
+import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.annotation.Transient;
+import org.springframework.data.annotation.TypeAlias;
+import org.springframework.data.annotation.Version;
+import org.springframework.data.couchbase.core.mapping.Document;
 
 /**
  * User entity for tests

src/test/java/org/springframework/data/couchbase/repository/query/StringN1qlQueryCreatorMockedTests.java

@@ -85,7 +85,7 @@ void createsQueryCorrectly() throws Exception {
 
 		Query query = creator.createQuery();
 		assertEquals(
-				"SELECT META(`travel-sample`).id AS __id, META(`travel-sample`).cas AS __cas, `firstname`, `lastname`, `createdBy`, `createdDate`, `lastModifiedBy`, `lastModifiedDate` FROM `travel-sample` where `_class` = \"org.springframework.data.couchbase.domain.User\" and firstname = $1 and lastname = $2",
+				"SELECT META(`travel-sample`).id AS __id, META(`travel-sample`).cas AS __cas, `_class`, `createdBy`, `createdDate`, `lastModifiedBy`, `lastModifiedDate`, `firstname`, `lastname`, `subtype` FROM `travel-sample` where `_class` = \"abstractuser\" and firstname = $1 and lastname = $2",
 				query.toN1qlSelectString(couchbaseTemplate.reactive(), User.class, false));
 	}
 
@@ -104,7 +104,7 @@ void createsQueryCorrectly2() throws Exception {
 
 		Query query = creator.createQuery();
 		assertEquals(
-				"SELECT META(`travel-sample`).id AS __id, META(`travel-sample`).cas AS __cas, `firstname`, `lastname`, `createdBy`, `createdDate`, `lastModifiedBy`, `lastModifiedDate` FROM `travel-sample` where `_class` = \"org.springframework.data.couchbase.domain.User\" and (firstname = $first or lastname = $last)",
+				"SELECT META(`travel-sample`).id AS __id, META(`travel-sample`).cas AS __cas, `_class`, `createdBy`, `createdDate`, `lastModifiedBy`, `lastModifiedDate`, `firstname`, `lastname`, `subtype` FROM `travel-sample` where `_class` = \"abstractuser\" and (firstname = $first or lastname = $last)",
 				query.toN1qlSelectString(couchbaseTemplate.reactive(), User.class, false));
 	}