Respect WithWrappingToken for all secret ID's in approle auth

[averche]

Background

When authenticating with vault via AppRole, the secret ID can be specified in one of 3 ways:

• FromFile
• FromEnv
• FromString

If the secret ID happens to be a wrapping token, the option auth.WithWrappingToken() will let the client know to treat it as such. However, the current implementation will only respect auth.WithWrappingToken() if the secret ID is specified from a file (FromFile) and silently fails otherwise, which could be surprising to callers.

The rationale behind this was that the wrapping token should be provided through a trusted orchestrator and is typically written to a file. However, it is conceivable that the trusted orchestrator would write it to an environment variable instead.

Solution

This PR will respect the auth.WithWrappingToken() for all secret ID's (whether specified via FromFile, FromEnv or FromString)

[hashicorp-cla]

All committers have signed the CLA.

[digivava]

Awesome, thank you! Just one comment with something optional, but looks good to go otherwise.