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##### SUMMARY
Allow to specify a new "format" parameter in "openssl_privatekey". Today the output format is decided by a very simple heuristic which requires further commands to work properly.
I need, for example, to generate a RSA private key but in PKCS8 format. The current heuristic uses OpenSSH format for RSA keys and only uses PKCS8 for Ed25519 and similar. This makes me use a "command" with "openssl" to convert the generated key, which leads to idempotency problems and unnecessary complexity.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
openssl_privatekey

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
The current heuristic should be kept unless overwritten by user.

<!--- Paste example playbooks or commands between quotes below -->
```yaml
openssl_privatekey:
  path: /etc/ssl/private/ansible.com.pem
  format: pkcs8
```
The values allowed are `pkcs1`, `raw` and `pkcs8`

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try:
                    crypto.load_privatekey(crypto.FILETYPE_PEM,
                                           priv_key_detail,
                                           to_bytes('y' if passphrase == 'x' else 'x'))
                    if passphrase is not None:
                        
                        
                        raise OpenSSLBadPassphraseError('Passphrase provided, but private key is not password-protected!')
                except crypto.Error as e:
                    if passphrase is None and len(e.args) > 0 and len(e.args[0]) > 0:
                        if e.args[0][0][2] in ('bad decrypt', 'bad password read'):
                            
                            
                            raise OpenSSLBadPassphraseError('No passphrase provided, but private key is password-protected!')
        elif backend == 'cryptography':
            try:
                result = load_pem_private_key(priv_key_detail,
                                              None if passphrase is None else to_bytes(passphrase),
                                              cryptography_backend())
            except TypeError as dummy:
                raise OpenSSLBadPassphraseError('Wrong or empty passphrase provided for private key')
            except ValueError as dummy:
                raise OpenSSLBadPassphraseError('Wrong passphrase provided for private key')
        return result
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)
def load_certificate(path, backend='pyopenssl'):