### 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
'description',
        'host',
        'port',
        'is_encrypted',
        'is_extra_encrypted',
    ]
    add_columns = edit_columns = [
        'conn_id',
        'conn_type',
        'description',
        'host',
        'schema',
        'login',
        'password',
        'port',
        'extra',
    ] + extra_fields
    add_form = edit_form = ConnectionForm
    add_template = 'airflow/conn_create.html'
    edit_template = 'airflow/conn_edit.html'
    add_widget = ConnectionFormWidget
    edit_widget = ConnectionFormWidget
    base_order = ('conn_id', 'asc')
    @action('muldelete', 'Delete', 'Are you sure you want to delete selected records?', single=False)
    @auth.has_access(
        [
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_DAG),
        ]
    )
    def action_muldelete(self, items):