### 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_
# enab
        aws_client.s3.put_bucket_versioning(
            Bucket=bucket_dst, VersioningConfiguration={"Status": "Enabled"}
        )
        response = aws_client.s3.put_bucket_replication(
            ReplicationConfiguration=replication_config, Bucket=bucket_src
        )
        snapshot.match("put-bucket-replication", response)
        response = aws_client.s3.get_bucket_replication(Bucket=bucket_src)
        snapshot.match("get-bucket-replication", response)
    @markers.aws.validated
    def test_replication_config(
        self, s3_create_bucket, create_iam_role_with_policy, snapshot, aws_client
    ):
        snapshot.add_transformer(snapshot.transform.s3_api())
        snapshot.add_transformer(
            snapshot.transform.jsonpath(
                "$..ReplicationConfiguration.Role", "role", reference_replacement=False
            )
        )
        snapshot.add_transformer(
            snapshot.transform.jsonpath(
                "$..Destination.Bucket", "dest-bucket", reference_replacement=False
            )
        )
        snapshot.add_transformer(
            snapshot.transform.key_value("ID", "id", reference_replacement=False)
        )
        bucket_src = f"src-{short_uid()}"
        bucket_dst = f"dst-{short_uid()}"