**Description** 

Since sensitive informations in the connection object (specifically the extras field) are now being masked based on sensitive key names, we should consider adding some common sensitive key names.

`private_key` from [ssh connection](https://airflow.apache.org/docs/apache-airflow-providers-ssh/stable/connections/ssh.html) is an examples.

**Use case / motivation**

Extras field used to be blocked out entirely before the sensitive value masking feature (#15599).

[Before in 2.0.2](https://github.com/apache/airflow/blob/2.0.2/airflow/hooks/base.py#L78
) and [after in 2.1.0](https://github.com/apache/airflow/blob/2.1.0/airflow/hooks/base.py#L78
).

Extras field containing sensitive information now shown unless the key contains sensitive names.

**Are you willing to submit a PR?** 

@ashb has expressed interest in adding this.

airflow/utils/log/secrets_masker.py
"""
        Redact an any secrets found in ``item``, if it is a string.
        If ``name`` is given, and it's a "sensitive" name (see
        :func:`should_hide_value_for_key`) then all string values in the item
        is redacted.
        """
        try:
            if name and should_hide_value_for_key(name):
                return self._redact_all(item)
            if isinstance(item, dict):
                return {dict_key: self.redact(subval, dict_key) for dict_key, subval in item.items()}
            elif isinstance(item, str):
                if self.replacer:
                    
                    
                    
                    return self.replacer.sub('***', item)
                return item
            elif isinstance(item, (tuple, set)):
                
                return tuple(self.redact(subval) for subval in item)
            elif isinstance(item, io.IOBase):
                return item