Escape clashing model names (OpenAPITools#6004)

Closes OpenAPITools#6002

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

@@ -235,9 +235,24 @@ public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> o
         this.updateOperationParameterEnumInformation(operations);
         this.addOperationObjectResponseInformation(operations);
         this.addOperationPrefixParameterInterfacesInformation(operations);
+        this.escapeOperationIds(operations);
         return operations;
     }
 
+    private void escapeOperationIds(Map<String, Object> operations) {
+        Map<String, Object> _operations = (Map<String, Object>) operations.get("operations");
+        List<CodegenOperation> operationList = (List<CodegenOperation>) _operations.get("operation");
+        for (CodegenOperation op : operationList) {
+            String param = op.operationIdCamelCase + "Request";
+            if (op.imports.contains(param)) {
+                // we import a model with the same name as the generated operation, escape it
+                op.operationIdCamelCase += "Operation";
+                op.operationIdLowerCase += "operation";
+                op.operationIdSnakeCase += "_operation";
+            }
+        }
+    }
+
     private void addOperationModelImportInfomation(Map<String, Object> operations) {
         // This method will add extra infomation to the operations.imports array.
         // The api template uses this infomation to import all the required