### Description

I bumped into a bug where a connection id was suffixed with a whitespace e.g. "myconn ". When referencing the connection id "myconn" (without whitespace), you get a connection not found error.

To avoid such human errors, I suggest restricting the characters allowed for connection ids.

Some suggestions:
- There's an `airflow.utils.helpers.validate_key` function for validating the DAG id. Probably a good idea to reuse this.
- I believe variable ids are also not validated, would be good to check those too.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] 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)

"""Test Duplicate multiple connection with suffix"""
    conn1 = Connection(
        conn_id="test_duplicate_gcp_connection",
        conn_type="Google Cloud",
        description="Google Cloud Connection",
    )
    conn2 = Connection(
        conn_id="test_duplicate_mysql_connection",
        conn_type="FTP",