### 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
return redirect(url_for('Airflow.index'))
        task = copy.copy(dag.get_task(task_id))
        task.resolve_template_files()
        ti: Optional[TaskInstance] = (
            session.query(TaskInstance)
            .options(
                
                
                
                joinedload(TaskInstance.queued_by_job, innerjoin=False),
                joinedload(TaskInstance.trigger, innerjoin=False),
            )
            .join(TaskInstance.dag_run)
            .filter(
                DagRun.execution_date == dttm,
                TaskInstance.dag_id == dag_id,
                TaskInstance.task_id == task_id,
            )
            .one_or_none()
        )
        if ti is None:
            ti_attrs: Optional[List[Tuple[str, Any]]] = None
        else:
            ti.refresh_from_task(task)
            all_ti_attrs = ((name, getattr(ti, name)) for name in dir(ti) if not name.startswith("_"))
            ti_attrs = sorted((name, attr) for name, attr in all_ti_attrs if not callable(attr))
        attr_renderers = wwwutils.get_attr_renderer()
        task_attrs = [
            (attr_name, attr)
            for attr_name, attr in (