### Apache Airflow version

2.2.0

### Operating System

Debian buster

### Versions of Apache Airflow Providers

_No response_

### Deployment

Astronomer

### Deployment details

astro dev start

### What happened

When I have tried to duplicate a connection first time it has created a connection with hello_copy1 and duplicating the same connection second time giving me an error of 
```Connection hello_copy2 can't be added. Integrity error, probably unique constraint.```




### What you expected to happen

It should create a connection with name hello_copy3 or the error message should be more user friendly.

### How to reproduce

https://github.com/apache/airflow/pull/15574#issuecomment-912438705

### Anything else

Suggested Error 
```
Connection hello_copy2 can't be added because it already exists.
```
or
Change the number logic in _copyN so the new name will be always unique.


### Are you willing to submit 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
"""Decorator for actions which verifies you have DAG edit access on the given tis/drs."""
    @wraps(action_func)
    def check_dag_edit_acl_for_actions(
        self,
        items: Optional[Union[List[TaskInstance], List[DagRun], TaskInstance, DagRun]],
        *args,
        **kwargs,
    ) -> None:
        if items is None:
            dag_ids: Set[str] = set()
        elif isinstance(items, list):
            dag_ids = {item.dag_id for item in items if item is not None}
        elif isinstance(items, TaskInstance) or isinstance(items, DagRun):
            dag_ids = {items.dag_id}
        else:
            raise ValueError(
                "Was expecting the first argument of the action to be of type "
                "Optional[Union[List[TaskInstance], List[DagRun], TaskInstance, DagRun]]."
                f"Was of type: {type(items)}"
            )
        for dag_id in dag_ids:
            if not current_app.appbuilder.sm.can_edit_dag(dag_id):
                flash(f"Access denied for dag_id {dag_id}", "danger")
                logging.warning("User %s tried to modify %s without having access.", g.user.username, dag_id)
                return redirect(self.get_default_url())
        return action_func(self, items, *args, **kwargs)
    return check_dag_edit_acl_for_actions
class SlaMissModelView(AirflowModelView):
    """View to show SlaMiss table"""