### 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
'id',
        'classpath',
        'created_date',
        'triggerer_id',
    ]
    search_columns = [
        'id',
        'classpath',
        'created_date',
        'triggerer_id',
    ]
    
    base_order = ('id', 'created_date')
    formatters_columns = {
        'created_date': wwwutils.datetime_f('created_date'),
    }
class TaskInstanceModelView(AirflowPrivilegeVerifierModelView):
    """View to show records from TaskInstance table"""
    route_base = '/taskinstance'
    datamodel = AirflowModelView.CustomSQLAInterface(models.TaskInstance)  
    class_permission_name = permissions.RESOURCE_TASK_INSTANCE
    method_permission_name = {
        'list': 'read',
        'action_clear': 'edit',
        'action_muldelete': 'delete',
        'action_set_running': 'edit',
        'action_set_failed': 'edit',
        'action_set_success': 'edit',
        'action_set_retry': 'edit',
    }