fix(secretmanager): add role and fix secretPrefix

[migmartri]

• Exposes secret_prefix again fixing the regression. It does it by bubbling it up to the parent struct.
• Adds role property to initializer and use it in the vault client to check read or write permissions.

NOTE: These issues were noticed when connecting to a production instance of vault and realized that the a policy I created wasn't working since the system was trying to push secrets to a different path.

Closes #315