### 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
"""
    Adds `.can_edit`, `.can_trigger`, and `.can_delete` properties
    to DAG based on current user's permissions.
    Located in `views.py` rather than the DAG model to keep
    permissions logic out of the Airflow core.
    """
    if 'dag' in context:
        dag = context['dag']
        can_create_dag_run = current_app.appbuilder.sm.has_access(
            permissions.ACTION_CAN_CREATE, permissions.RESOURCE_DAG_RUN
        )
        dag.can_edit = current_app.appbuilder.sm.can_edit_dag(dag.dag_id)
        dag.can_trigger = dag.can_edit and can_create_dag_run
        dag.can_delete = current_app.appbuilder.sm.has_access(
            permissions.ACTION_CAN_DELETE,
            permissions.RESOURCE_DAG,
        )
        context['dag'] = dag
before_render_template.connect(add_user_permissions_to_dag)
class Airflow(AirflowBaseView):
    """Main Airflow application."""
    @expose('/health')
    def health(self):