### 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_
# retr
        resp = .get(url, verify=False)
        assert resp.status_code == 200
        assert to_str(resp.content) == "something"
        time.sleep(3)  # wait 
        resp = .get(url, verify=False)
        resp_content = to_str(resp.content)
        assert resp.status_code == 403
        exception = xmltodict.parse(resp.content)
        snapshot.match("expired-exception", exception)
        assert "<Code>AccessDenied</Code>" in resp_content
        assert "<Message>Request has expired</Message>" in resp_content
        url = presigned_client.generate_presigned_url(
            "get_",
            Params={"Bucket": s3_bucket, "Key": _key},
            ExpiresIn=120,
        )
        resp = .get(url, verify=False)
        assert resp.status_code == 200
        assert to_str(resp.content) == "something"
    @markers.aws.validated
    @pytest.mark.parametrize("signature_version", ["s3", "s3v4"])
    def test_s3_put_presigned_url_with_different_headers(
        self,
        s3_bucket,
        signature_version,
        snapshot,
        patch_s3_skip_signature_validation_false,
        aws_client,
        presigned_snapshot_transformers,