### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

- Localstack fails with HTTP 500, error code "InternalError", message "not enough values to unpack (expected 2, got 1)" when `CopySource` is an invalid string for `copy_object` API.

### Expected Behavior

- For the same API `copy_object`, the cloud fails with HTTP 400, error code "InvalidArgument".
- Localstack should handle invalid `CopySource` i.e., it is a dictionary with one value or an invalid string not adhering to "{bucket}/{key}" format.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    botoclient.copy_object(CopySource="Invalid_random_string", Bucket="test_bucket", Key=key) 


 test_bucket is a valid bucket.  

### Environment

```markdown
- OS: Ubuntu 22.04.2 LTS
- LocalStack: 2.1.0
- boto3: 1.28.6
```


### Anything else?

_No response_
"StorageClass": StorageClass.STANDARD,
                "Metadata": {"foo": "bar-complicated-no-random"},
            },
        )
        assert StorageClass.STANDARD not in url
        assert "bar-complicated-no-random" not in url
        handler_file = os.path.join(
            os.path.dirname(__file__), "../lambda_/functions/lambda_s3_integration_presign.js"
        )
        temp_folder = create_tmp_folder_lambda(
            handler_file,
            run_command="npm i @aws-sdk/util-endpoints @aws-sdk/client-s3 @aws-sdk/s3-request-presigner @aws-sdk/middleware-endpoint",
        )
        function_name = f"func-integration-{short_uid()}"
        create_lambda_function(
            func_name=function_name,
            zip_file=testutil.create_zip_file(temp_folder, get_content=True),
            runtime=Runtime.nodejs14_x,
            handler="lambda_s3_integration_presign.handler",
            role=lambda_su_role,
            envvars={
                "ACCESS_KEY": s3_constants.DEFAULT_PRE_SIGNED_ACCESS_KEY_ID,
                "SECRET_KEY": s3_constants.DEFAULT_PRE_SIGNED_SECRET_ACCESS_KEY,
            },
        )
        s3_create_bucket(Bucket=function_name)
        response = aws_client.lambda_.invoke(FunctionName=function_name)
        payload = json.load(response["Payload"])
        presigned_url = payload["body"].strip('"')
        # asse