### Description

The stable REST API seems to be missing the functionality to delete a DAG. 
This would mirror clicking the "Trash Can" on the UI (and could maybe eventually power it)

![image](https://user-images.githubusercontent.com/80706212/131702280-2a8d0d74-6388-4b84-84c1-efabdf640cde.png)


### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/www/views.py
"""Multiple delete."""
        self.datamodel.delete_all(items)
        self.update_redirect()
        return redirect(self.get_redirect())
    @action(
        'mulduplicate',
        'Duplicate',
        'Are you sure you want to duplicate the selected connections?',
        single=False,
    )
    @provide_session
    @auth.has_access(
        [
            (permissions.ACTION_CAN_CREATE, permissions.RESOURCE_CONNECTION),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_CONNECTION),
        ]
    )
    def action_mulduplicate(self, connections, session=None):
        """Duplicate Multiple connections"""
        for selected_conn in connections:
            new_conn_id = selected_conn.conn_id