### 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_
snapshot.add_transformer(snapshot.transform.key_value("VersionId"))
        bucket_name = s3_create_bucket(LockEnabledForBucket=True)
        _key = "default-"
        put_lock_config = aws_client.s3.put__lock_configuration(
            Bucket=bucket_name,
            LockConfiguration={
                "LockEnabled": "Enabled",
                "Rule": {
                    "DefaultRetention": {
                        "Mode": "GOVERNANCE",
                        "Days": 1,
                    }
                },
            },
        )
        snapshot.match("put-lock-config", put_lock_config)
        put_locked__default = aws_client.s3.put_(
            Bucket=bucket_name,
            Key=_key,
            Body="test-default-lock",
        )
        snapshot.match("put--default", put_locked__default)
        head_ = aws_client.s3.head_(Bucket=bucket_name, Key=_key)
        snapshot.match("head--default", head_)
        # add 
        # afte
        last_modified_and_one_day = head_["LastModified"] + datetime.timedelta(days=1)
        delta_2_min = datetime.timedelta(minutes=2)  # to a
        assert (