Enable changing the provider for X509 certificate

[gyakami]

Description

The provider used for issuing X509 certificates is currently fixed to BC. We have added a new property to allow changing this provider. Depending on the provider used, the RSAPrivateCrtKey interface might not be implemented. In such cases, casting will fail and an error will occur. Therefore, as a workaround, we have added the ATHENZ_CRYPTO_AUTHORITY_KEY_IDENTIFIER property to allow selecting whether to add the AUTHORITY KEY IDENTIFIER as an extension.

athenz/libs/java/auth_core/src/main/java/com/yahoo/athenz/auth/util/Crypto.java

Line 742 in 4d18d62

RSAPrivateCrtKey rsaCrtKey = (RSAPrivateCrtKey) privateKey;

Contribution Checklist:

• The pull request does not introduce any breaking changes
• I have read the contribution guidelines.
• Create an issue and link to the pull request.

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