### 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_
# mimi
        # http
        policy = {
            "Id": "test-s3-bucket-access",
            "Version": "2012-10-17",
            "Statement": [
                {
                    "Sid": "AllowSSLRequestsOnly",
                    "Action": "s3:*",
                    "Effect": "Deny",
                    "Resource": [f"arn:aws:s3:::{s3_bucket}", f"arn:aws:s3:::{s3_bucket}/*"],
                    "Condition": {"Bool": {"aws:SecureTransport": "false"}},
                    "Principal": "*",
                }
            ],
        }
        aws_client.s3.put_bucket_policy(Bucket=s3_bucket, Policy=json.dumps(policy))
        # put 
        content = b"test-content"
        aws_client.s3.put_(Bucket=s3_bucket, Key="test/123", Body=content)
        result = aws_client.s3.get_(Bucket=s3_bucket, Key="test/123")
        received_content = result["Body"].read()
        assert received_content == content
        # enab
        monkeypatch.setattr(s3_constants, "ENABLE_MOTO_BUCKET_POLICY_ENFORCEMENT", True)
        with pytest.raises(ClientError) as exc:
            aws_client.s3.get_(Bucket=s3_bucket, Key="test/123")
        assert exc.value.response["Error"]["Code"] == "403"
        assert exc.value.response["Error"]["Message"] == "Forbidden"
class TestS3BucketLifecycle: