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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`

<!--- HINT: You can also paste gist.github.com links for larger files -->

'2.23.42.0.78': ('setct-CertReqTBEX', ),
    '2.23.42.0.79': ('setct-CertResTBE', ),
    '2.23.42.0.80': ('setct-CRLNotificationTBS', ),
    '2.23.42.0.81': ('setct-CRLNotificationResTBS', ),
    '2.23.42.0.82': ('setct-BCIDistributionTBS', ),
    '2.23.42.1': ('message extensions', 'set-msgExt'),
    '2.23.42.1.1': ('generic cryptogram', 'setext-genCrypt'),
    '2.23.42.1.3': ('merchant initiated auth', 'setext-miAuth'),
    '2.23.42.1.4': ('setext-pinSecure', ),
    '2.23.42.1.5': ('setext-pinAny', ),
    '2.23.42.1.7': ('setext-track2', ),
    '2.23.42.1.8': ('additional verification', 'setext-cv'),
    '2.23.42.3': ('set-attr', ),
    '2.23.42.3.0': ('setAttr-Cert', ),
    '2.23.42.3.0.0': ('set-rootKeyThumb', ),
    '2.23.42.3.0.1': ('set-addPolicy', ),
    '2.23.42.3.1': ('payment gateway capabilities', 'setAttr-PGWYcap'),
    '2.23.42.3.2': ('setAttr-TokenType', ),
    '2.23.42.3.2.1': ('setAttr-Token-EMV', ),
    '2.23.42.3.2.2': ('setAttr-Token-B0Prime', ),
    '2.23.42.3.3': ('issuer capabilities', 'setAttr-IssCap'),
    '2.23.42.3.3.3': ('setAttr-IssCap-CVM', ),
    '2.23.42.3.3.3.1': ('generate cryptogram', 'setAttr-GenCryptgrm'),
    '2.23.42.3.3.4': ('setAttr-IssCap-T2', ),
    '2.23.42.3.3.4.1': ('encrypted track 2', 'setAttr-T2Enc'),
    '2.23.42.3.3.4.2': ('cleartext track 2', 'setAttr-T2cleartxt'),
    '2.23.42.3.3.5': ('setAttr-IssCap-Sig', ),
    '2.23.42.3.3.5.1': ('ICC or token signature', 'setAttr-TokICCsig'),
    '2.23.42.3.3.5.2': ('secure device signature', 'setAttr-SecDevSig'),
    '2.23.42.5': ('set-policy', ),