**Description**

Replace the Configuration JSON text-area with a form that has individual input fields for each key & value. This will remove the need for the user to provide a json object. See hashicorp vault's key-value secrets UI for an example of what this might look like:

![Screenshot 2020-09-21 at 12 06 03](https://user-images.githubusercontent.com/17148324/93759844-df04f680-fc02-11ea-8613-f3bcc0b22d09.png)
 
- If present these keys and values should be serialised as json client-side and posted to the trigger-dag API endpoint as the `conf` request-parameter.
- By default no conf request-parameter is sent. Perhaps a checkbox should be used to determine whether conf is sent at all?
- The user may want to add new keys, or remove keys & values that they have previously added.
- [PR-10839](https://github.com/apache/airflow/pull/10839) is pre-populating the form with the DAG's default params. The new form should be pre-populated with the keys & values from `DAG.params`


**Use case / motivation**

Currently when triggering a manual DAG run with user-provided runtime parameters, the user has to provide a correctly formatted JSON object. Filling in a form with keys & values will be a significantly better user experience, and will be less error prone & laborious than handling json in a free-text field.

This builds on the great work already done on enhancing the Trigger-DAG functionality

**Related Issues**

Originating PR: https://github.com/apache/airflow/pull/10839
"""Multiple delete action."""
        self.datamodel.delete_all(items)
        self.update_redirect()
        return redirect(self.get_redirect())
    @action(
        "mulnotificationsent",
        "Set notification sent to true",
        "Are you sure you want to set all these notifications to sent?",
        single=False,
    )
    def action_mulnotificationsent(self, items: list[SlaMiss]):
        return self._set_notification_property(items, "notification_sent", True)
    @action(
        "mulnotificationsentfalse",
        "Set notification sent to false",
        "Are you sure you want to mark these SLA alerts as notification not sent yet?",
        single=False,
    )
    def action_mulnotificationsentfalse(self, items: list[SlaMiss]):
        return self._set_notification_property(items, "notification_sent", False)
    @action(
        "mulemailsent",
        "Set email sent to true",
        "Are you sure you want to mark these SLA alerts as emails were sent?",
        single=False,
    )
    def action_mulemailsent(self, items: list[SlaMiss]):