### 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_
# AWS 
        # the 
        # http
        # hand
        # http
        # TODO
        snapshot.add_transformer(snapshot.transform.s3_api())
        # put 
        short_expire = datetime.datetime.now(ZoneInfo("GMT")) + datetime.timedelta(seconds=1)
        _key_expired = "key--expired"
        _key_not_expired = "key--not-expired"
        aws_client.s3.put_(
            Bucket=s3_bucket,
            Key=_key_expired,
            Body="foo",
            Expires=short_expire,
        )
        # slee
        time.sleep(3)
        # head
        response = aws_client.s3.head_(Bucket=s3_bucket, Key=_key_expired)
        assert response["Expires"] < datetime.datetime.now(ZoneInfo("GMT"))
        snapshot.match("head--expired", response)
        # try 
        if not is_aws_cloud():  # fixm