Do not add schema / class name mapping where custom mapping exists (#14984)

* fix #13150 Do not add schema / class name mapping where custom mapping exists

* update test spec

* improve import

* fix import for mapped models

* fix python

* code clean up

* fix dart client import

* fix dart:core import

* better import

* add tests

---------

Co-authored-by: Bernie Schelberg <bernard.schelberg@mywave.ai>

samples/client/petstore/java/webclient/api/openapi.yaml

@@ -1507,6 +1507,9 @@ components:
       - $ref: '#/components/schemas/Cat_allOf'
     Animal:
       discriminator:
+        mapping:
+          DOG: '#/components/schemas/Dog'
+          CAT: '#/components/schemas/Cat'
         propertyName: className
       properties:
         className:

samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java

@@ -23,8 +23,6 @@ import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import com.fasterxml.jackson.annotation.JsonValue;
-import org.openapitools.client.model.Cat;
-import org.openapitools.client.model.Dog;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import com.fasterxml.jackson.annotation.JsonTypeName;
 
@@ -42,8 +40,8 @@ import com.fasterxml.jackson.annotation.JsonTypeName;
 )
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
-  @JsonSubTypes.Type(value = Cat.class, name = "Cat"),
-  @JsonSubTypes.Type(value = Dog.class, name = "Dog"),
+  @JsonSubTypes.Type(value = Cat.class, name = "CAT"),
+  @JsonSubTypes.Type(value = Dog.class, name = "DOG"),
 })
 
 public class Animal {