Issues with RSA public key

Hi,

Thank yoy soo much for your time spent on this project, looking forward exploring it some more.

I had a quick question regarding the use of this library and it's something I've been struggeling with for a while now.

```
let rsa_pub = RsaPublicKey::from_public_key_pem(&response.pem)
.map_err(|e| format!("RSA PEM parse error: {:?}", e))
.unwrap();

let pkcs1_der_document = rsa_pub
.to_pkcs1_der()
.map_err(|e| anyhow::anyhow!("PKCS#1 DER encode error: {}", e))?;

let result = KSMPublicKey {
id: Sha256::digest(response.name.as_bytes()).to_vec(),
label: response.name,
algorithm: KeyAlgorithm::Rsa,
der: pkcs1_der_document.into_vec(),
};
```

Is this correct?

Getting weird error message when using pkcs11-tool

```
warning: PKCS11 function C_GetAttributeValue(MODULUS_BITS) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12)
warning: PKCS11 function C_GetAttributeValue(ENCRYPT) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12)
warning: PKCS11 function C_GetAttributeValue(VERIFY) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12)
warning: PKCS11 function C_GetAttributeValue(VERIFY_RECOVER) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12)
warning: PKCS11 function C_GetAttributeValue(WRAP) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12)
```

Based on the info I can see in the attributes.rs file these values should be injected automatically but maybe I'm missing something?

Should I also implement any more `C_*` functions other than `C_GetFunctionList` ?

Currently building a GCP KMS module that is mostly working but there are still some weird edge cases I need to solve.

Thank you