### 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)

tests/www/views/test_views_connection.py
#
#
#
import json
from unittest import mock
import pytest
from airflow.models import Connection
from airflow.utils.session import create_session
from airflow.www.extensions import init_views
from airflow.www.views import ConnectionModelView
from tests.test_utils.www import check_content_in_response
CONNECTION = {
    'conn_id': 'test_conn',
    'conn_type': 'http',
    'description': 'description',
    'host': 'localhost',
    'port': 8080,
    'username': 'root',
    'password': 'admin',
}
@pytest.fixture(autouse=True)
def clear_connections():
    with create_session() as session:
        session.query(Connection).delete()
def test_create_connection(admin_client):