VaultTokenCredentialBinding should create child tokens if limited policies are configured

[bluesliverx]

What feature do you want to see added?

The VaultTokenCredentialBinding creates tokens that have full permission from the credential when policies are configured. If policies are configured on the folder or global config, a child token should be created that has those policies only in order to limit access to secrets.

This change should not be very big as it can utilize a lot of the same code built into the vault accessor class to create child tokens when necessary.

Upstream changes

n/a

Are you interested in contributing this feature?

Yes, I already have a PR (#338) created to add this functionality.