### 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, domain, use_virtual_address, aws_client, region_name
    ):
        """Assert that /favicon.ico s can be created/accessed/deleted using amazonaws host headers"""
        s3_key = "favicon.ico"
        content = b"test 123"
        aws_client.s3.put_(Bucket=s3_bucket, Key=s3_key, Body=content)
        aws_client.s3.head_(Bucket=s3_bucket, Key=s3_key)
        path = s3_key if use_virtual_address else f"{s3_bucket}/{s3_key}"
        url = f"{config.internal_service_url()}/{path}"
        headers = mock_aws_request_headers(
            "s3",
            aws_access_key_id=TEST_AWS_ACCESS_KEY_ID,
            region_name=region_name,
        )
        headers["host"] = f"{s3_bucket}.{domain}" if use_virtual_address else domain
        # get 
        result = .get(url, headers=headers)
        assert result.ok
        assert result.content == content
        # dele
        result = .delete(url, headers=headers)
        assert result.ok
        # asse
        with pytest.raises(ClientError) as exc:
            aws_client.s3.head_(Bucket=s3_bucket, Key=s3_key)
        assert exc.value.response["Error"]["Message"] == "Not Found"
class TestS3BucketPolicies: