Document design decisions here.
For now we have decided LogGroupName should be a required property for simplicity. A future enhancement could make this optional and create a new CloudWatch Log Group when not provided. Users could Ref the resource if we exposed/documented the resource naming convention.
Decided FilterPattern should be a required property so as not to provide a footgun to users. If this were to default to "", noisy logs could invoke hundreds/thousands of Lambda functions in short periods of time.