Consumers can now request private keys (for SSH certificates) protected by a passphrase

[achuchev]

• The PrivateKeyPassphrase attribute was missing, so consumers cannot request private keys protected by a passphrase.
• Remove PrivateKeyFormat from the SSH cert data structure. This option has never been implemented on the server side.

[luispresuelVenafi]

Changes looks good @achuchev , could you add a unit test for this?

[achuchev]

@luispresuelVenafi Do you mind to point me where I can find similar tests?

[luispresuelVenafi]

Sure @achuchev, you could take this test as an example: https://github.com/Venafi/vcert/blob/master/pkg/venafi/tpp/connector_test.go#L2107

You could do the following tests:

• Provide the passphrase in the request and after the retrieve operation, that passphrase still works for opening the private key.
• Negative test: Provide a passphrase in the request and try to open the private key without providing the passphrase; it should fail.