### 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_
"Format": "CSV",
                    }
                },
                "IsEnabled": True,
                "IncludedVersions": "All",
                "Schedule": {"Frequency": "Daily"},
            }
            aws_client.s3.put_bucket_inventory_configuration(
                Bucket=src_bucket,
                Id=config_id,
                InventoryConfiguration=inventory_configuration,
            )
        for inv_config_id in ("test-1", "z-test", "a-test"):
            _put_bucket_inventory_configuration(inv_config_id)
        list_inv_configs = aws_client.s3.list_bucket_inventory_configurations(Bucket=src_bucket)
        snapshot.match("list-inventory-config", list_inv_configs)
        del_inv_config = aws_client.s3.delete_bucket_inventory_configuration(
            Bucket=src_bucket,
            Id="z-test",
        )
        snapshot.match("del-inventory-config", del_inv_config)
        list_inv_configs = aws_client.s3.list_bucket_inventory_configurations(Bucket=src_bucket)
        snapshot.match("list-inventory-config-after-del", list_inv_configs)
    @pytest.mark.parametrize(
        "use_virtual_address",
        [True, False],
    )
    @markers.snapshot.skip_snapshot_verify(paths=["$..x-amz-server-side-encryption"])
    @markers.aws.validated
    def test_get__content_length_with_virtual_host(