Add a new field to identified sealed docket entries.

[ERosendo]

We propose adding a new field to the Docket entries model to mark identified sealed entries. This field could be a boolean flag, similar to the "is_sealed" field in the RECAPDocument model, offering a more transparent and efficient way to track them.

Currently, we must delete the docket entries once they are identified as sealed. However, Introducing a flag would allow us to retain sealed docket entry records while indicating their restricted status.