reuse 1 open api schema for everything. Add also case where interface extends interface.

Author: Picazsoo

bin/configs/kotlin-spring-boot-x-kotlin-implements.yaml

@@ -1,7 +1,7 @@
 generatorName: kotlin-spring
 outputDir: samples/server/petstore/kotlin-springboot-x-kotlin-implements
 library: spring-boot
-inputSpec: modules/openapi-generator/src/test/resources/2_0/petstore-x-kotlin-implements.yaml
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/petstore-with-x-kotlin-implements.yaml
 templateDir: modules/openapi-generator/src/main/resources/kotlin-spring
 additionalProperties:
   documentationProvider: none

modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/spring/KotlinSpringServerCodegenTest.java

@@ -977,12 +977,12 @@ public void generateSerializableModelWithXimplements() throws Exception {
 
         generator.opts(input).generate();
 
-        Path path = Paths.get(outputPath + "/src/main/kotlin/org/openapitools/model/Pet.kt");
+        Path path = Paths.get(outputPath + "/src/main/kotlin/org/openapitools/model/Dog.kt");
         assertFileContains(
                 path,
                 "import java.io.Serializable",
-                "@get:JsonProperty(\"name\", required = true) override val name: kotlin.String,",
-                ") : Serializable, com.some.package.Named {",
+                "@get:JsonProperty(\"likesFetch\", required = true) override val likesFetch: kotlin.Boolean,",
+                ") : Pet, Serializable,  com.some.pack.Fetchable {",
                 "private const val serialVersionUID: kotlin.Long = 1"
         );
     }
@@ -1009,17 +1009,17 @@ public void generateNonSerializableModelWithXimplements() throws Exception {
 
         generator.opts(input).generate();
 
-        Path path = Paths.get(outputPath + "/src/main/kotlin/org/openapitools/model/Pet.kt");
+        Path path = Paths.get(outputPath + "/src/main/kotlin/org/openapitools/model/Dog.kt");
         assertFileContains(
                 path,
-                "@get:JsonProperty(\"name\", required = true) override val name: kotlin.String,",
-                ") : com.some.package.Named {"
+                "@get:JsonProperty(\"likesFetch\", required = true) override val likesFetch: kotlin.Boolean,",
+                ") : Pet, com.some.pack.Fetchable {"
         );
         assertFileNotContains(
                 path,
                 "import java.io.Serializable",
-                ") : Serializable, com.some.package.Named {",
-                ") : Serializable {",
+                ") : Pet, Serializable,  com.some.pack.Fetchable {",
+                ") : Pet, Serializable {",
                 "private const val serialVersionUID: kotlin.Long = 1"
         );
     }