**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
"""Duplicate Multiple connections"""
        for selected_conn in connections:
            new_conn_id = selected_conn.conn_id
            match = re.search(r"_copy(\d+)$", selected_conn.conn_id)
            base_conn_id = selected_conn.conn_id
            if match:
                base_conn_id = base_conn_id.split("_copy")[0]
            potential_connection_ids = [f"{base_conn_id}_copy{i}" for i in range(1, 11)]
            query = session.query(Connection.conn_id).filter(Connection.conn_id.in_(potential_connection_ids))
            found_conn_id_set = {conn_id for conn_id, in query}
            possible_conn_id_iter = (
                connection_id
                for connection_id in potential_connection_ids
                if connection_id not in found_conn_id_set
            )
            try:
                new_conn_id = next(possible_conn_id_iter)
            except StopIteration:
                flash(
                    f"Connection {new_conn_id} can't be added because it already exists, "
                    f"Please rename the existing connections",
                    "warning",
                )
            else:
                dup_conn = Connection(
                    new_conn_id,
                    selected_conn.conn_type,
                    selected_conn.description,
                    selected_conn.host,