### 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
table = [
                (section, key, value, source)
                for section, parameters in conf.as_dict(True, True).items()
                for key, (value, source) in parameters.items()
            ]
        else:
            config = (
                "# Your Airflow administrator chose not to expose the "
                "configuration, most likely for security reasons."
            )
            table = None
        if raw:
            return Response(response=config, status=200, mimetype="application/text")
        else:
            code_html = Markup(
                highlight(
                    config,
                    lexers.IniLexer(),  
                    HtmlFormatter(noclasses=True),
                )
            )
            return self.render_template(
                'airflow/config.html',
                pre_subtitle=settings.HEADER + "  v" + airflow.__version__,
                code_html=code_html,
                title=title,
                subtitle=subtitle,
                table=table,
            )
class RedocView(AirflowBaseView):