Enable useOneOfInterfaces for the ruby generator (#8061)

Tested against https://ftc-events.firstinspires.org/swagger/v2.0/swagger.json

Used to generate un-runnable code, now it works

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -622,6 +622,7 @@ public class DefaultCodegen implements CodegenConfig {
      *
      * @param objs Map of models
      * @return maps of models with better enum support
+     * 
      */
     public Map<String, Object> postProcessModelsEnum(Map<String, Object> objs) {
         List<Object> models = (List<Object>) objs.get("models");
@@ -6473,6 +6474,7 @@ public class DefaultCodegen implements CodegenConfig {
         cm.classname = type;
         cm.vendorExtensions.put("x-is-one-of-interface", true);
         cm.interfaceModels = new ArrayList<CodegenModel>();
+        cm.classFilename = toModelFilename(type);
 
         addOneOfInterfaces.add(cm);
     }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java

@@ -92,6 +92,7 @@ public class RubyClientCodegen extends AbstractRubyCodegen {
         );
 
         supportsInheritance = true;
+        useOneOfInterfaces = true;
 
         // clear import mapping (from default generator) as ruby does not use it
         // at the moment