### 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_
self, s3_bucket, case_sensitive_headers, aws_client
    ):
        # Test 
        _key = "key-by-hostname"
        aws_client.s3.put_(Bucket=s3_bucket, Key=_key, Body="something")
        # get 
        case_sensitive_before = http2_server.RETURN_CASE_SENSITIVE_HEADERS
        try:
            url = aws_client.s3.generate_presigned_url(
                "get_", Params={"Bucket": s3_bucket, "Key": _key}
            )
            http2_server.RETURN_CASE_SENSITIVE_HEADERS = case_sensitive_headers
            response = .get(url, verify=False)
            # expe
            header_names = list(response.headers.keys())
            expected_etag = "ETag" if case_sensitive_headers else "etag"
            assert expected_etag in header_names
        finally:
            http2_server.RETURN_CASE_SENSITIVE_HEADERS = case_sensitive_before
    @pytest.mark.parametrize(
        "signature_version, use_virtual_address",
        [
            ("s3", False),
            ("s3", True),
            ("s3v4", False),
            ("s3v4", True),
        ],
    )
    @markers.aws.validated
    def test_presigned_url_signature_authentication_expired(