Extend the BaseRepository to support: delete

The function is for deleting the entity in the database.

The function signature should like:

```
delete(object: T>: T
```

Some the subclass can do:

```
TokenRepository.delete(token)
```

Possible edge cases:

* Can not find the entity by id. (404 with error message)
* Maybe there are some cases that database will throw error like, foreign key violation, we should translate this type of exception to : (500, database exception)
* Our rule for deletion is that we don't really delete the record, but set the `active` field to `false`

---

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