add pets union test yml file

tests/Kiota.Builder.Tests/OpenApiSampleFiles/PetsUnion.cs

@@ -0,0 +1,66 @@
+namespace Kiota.Builder.Tests.OpenApiSampleFiles;
+
+
+public static class PetsUnion
+{
+    public static readonly string OpenApiYaml = @"
+openapi: 3.0.0
+info:
+  title: Pet API
+  version: 1.0.0
+paths:
+  /pets:
+    patch:
+      summary: Update a pet
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              oneOf:
+                - $ref: '#/components/schemas/Cat'
+                - $ref: '#/components/schemas/Dog'
+              discriminator:
+                propertyName: pet_type
+      responses:
+        '200':
+          description: Updated
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+        - pet_type
+      properties:
+        pet_type:
+          type: string
+      discriminator:
+        propertyName: pet_type
+    Dog:     
+      allOf: 
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            bark:
+              type: boolean
+            breed:
+              type: string
+              enum: [Dingo, Husky, Retriever, Shepherd]
+      required:
+        - pet_type
+        - bark
+        - breed
+    Cat:     
+      allOf: 
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            hunts:
+              type: boolean
+            age:
+              type: integer
+      required:
+        - pet_type
+        - hunts
+        - age";
+}