### 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/api_connexion/endpoints/dag_endpoint.py
#
#
from flask import current_app, g, request
from marshmallow import ValidationError
from airflow import DAG
from airflow.api_connexion import security
from airflow.api_connexion.exceptions import BadRequest, NotFound
from airflow.api_connexion.parameters import check_limit, format_parameters
from airflow.api_connexion.schemas.dag_schema import (
    DAGCollection,
    dag_detail_schema,
    dag_schema,
    dags_collection_schema,
)
from airflow.exceptions import SerializedDagNotFound
from airflow.models.dag import DagModel
from airflow.security import permissions
from airflow.utils.session import provide_session
@security.requires_access([(permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG)])
@provide_session
def get_dag(dag_id, session):
    """Get basic information about a DAG."""
    dag = session.query(DagModel).filter(DagModel.dag_id == dag_id).one_or_none()
    if dag is None:
        raise NotFound("DAG not found", detail=f"The DAG with dag_id: {dag_id} was not found")
    return dag_schema.dump(dag)
@security.requires_access([(permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG)])
def get_dag_details(dag_id):