[FEATURE REQ] Feature parity with KeyVault Secret SDK for JCA

[chenrujun]

Context

Azure KeyVault JCA is the bridge between Azure KeyVault Certificate and JDK JCA API.

So the library should have same feature set as Azure KeyVault Certificate SDK from configuration perspective.

Including:

• Authentication methods
• Configurations
  • Proxy
• RetryPolicy
• Logging Options
• HttpOptions

And this JCA lib should consume the same environment as Azure KeyVault Certificate SDK does.

For example , SDK accepts AZURE_KEYVAULT_ENDPOINT environment to config endpoint, which should be takes by JCA lib as well.

Design

JCA is built with a homebrew Certificate Client instead of Azure SDK Certificate Client for fewer dependencies

but this design causes lots of issues so far, like:

• feature missing like the retry policy is not existing in JCA but a standard feature across all Azure SDKs
• incomplete authentication methods

so, in the new design:

• JCA on top of Azure SDK Certificate Client, no more homebrew client.
• Provide a shaded uber jar to avoid any classpath pollution.
• JCA should be extensible, user should be able to provide a CertificateClientBuilder or CertificateClient or CertificateAsyncClient to it