### 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
permissions.ACTION_CAN_READ,
        permissions.ACTION_CAN_ACCESS_MENU,
    ]
    list_columns = [
        'id',
        'dag_id',
        'run_id',
        'dag_run.execution_date',
        'task_id',
        'try_number',
        'start_date',
        'end_date',
        'duration',
        'reschedule_date',
    ]
    label_columns = {
        'dag_run.execution_date': 'Execution Date',
    }
    search_columns = [
        'dag_id',
        'task_id',
        'run_id',
        'execution_date',
        'start_date',
        'end_date',
        'reschedule_date',
    ]
    base_order = ('id', 'desc')
    base_filters = [['dag_id', DagFilter, lambda: []]]
    def duration_f(self):