### 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_
key = "my-key"
        transfer_config = TransferConfig(multipart_threshold=5 * KB, multipart_chunksize=1 * KB)
        def upload_file(size_in_kb: int):
            file = tmpdir / f"test-file-{short_uid()}.bin"
            data = b"1" * (size_in_kb * KB)
            file.write(data=data, mode="w")
            aws_client.s3.upload_file(
                Bucket=s3_bucket,
                Key=key,
                Filename=str(file.realpath()),
                ExtraArgs={"StorageClass": "DEEP_ARCHIVE"},
                Config=transfer_config,
            )
        upload_file(1)
        upload_file(9)
        upload_file(15)
        for obj in aws_client.s3.list_s_v2(Bucket=s3_bucket)["Contents"]:
            assert obj["StorageClass"] == "DEEP_ARCHIVE"
    @markers.aws.validated
    def test_s3_get_deep_archive__restore(self, s3_create_bucket, snapshot, aws_client):
        snapshot.add_transformer(snapshot.transform.s3_api())
        bucket_name = f"bucket-{short_uid()}"
        _key = f"key-{short_uid()}"
        s3_create_bucket(Bucket=bucket_name)
        # put 
        aws_client.s3.put_(
            Bucket=bucket_name,
            Key=_key,
            Body="body data",
            StorageClass="DEEP_ARCHIVE",