### 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_
"""
        This particular test validates the fix for localstack#7424
        Moto would still validate with the `host` header if buckets where subdomain based even though in the new ASF
        provider, every request was forwarded by the VirtualHost proxy.
        """
        s3_http_client = aws_http_client_factory("s3", signer_factory=SigV4Auth)
        endpoint_url = _endpoint_url()
        # this 
        resp = s3_http_client.get(endpoint_url)
        assert resp.ok
        assert b"<Bucket" in resp.content
        # the 
        resp = s3_http_client.get(endpoint_url, headers={"host": "aws.test.local"})
        assert resp.ok
        assert b"<Bucket" in resp.content
    @pytest.mark.skipif(condition=TEST_S3_IMAGE, reason="Lambda not enabled in S3 image")
    @markers.skip_offline
    @markers.aws.validated
    @markers.snapshot.skip_snapshot_verify(
        condition=is_v2_provider,
        paths=["$..ServerSideEncryption"],
    )
    def test_s3_lambda_integration(
        self,
        create_lambda_function,
        lambda_su_role,
        s3_create_bucket,