Feature request: Implement vault-java-driver's Vault.prefixPathDepth parameter

[Dugong42]

Summary

Hi, this issue concerns the Hashicorp Vault provider.

The Vault provider currently supports a vault.prefixpath parameter. This parameter is used by vault-java-driver in a way that is non-intuitive regarding its name.

Motivation

The driver's VaultConfig.prefixPath (string) parameter is not used as an actual prefix by the driver.
Instead, it is used to determine the path depth (levels of forward slashes) at which a "/data" key is inserted in the case of kv v2 secrets. This non-intuitive feature is somewhat documented in the javadoc and I've created the #246 PR to document it here as well to help client integration.

Meanwhile the VaultConfig.prefixPathDepth (number) parameter is clearly documented with examples in the driver's README. It has a name coherent with its usage which does not depend on an implicit behaviour. IMHO this parameter should be available as the preferred solution.

Proposed solution

I suggest that a vault.prefixpathdepth parameter (mapped to VaultConfig.prefixPathDepth) be implemented as an optional alternative to vault.prefixpath.