auth: adds option to enable verbose logging during sso

[mismithhisler]

Description

Adds the ability to enable a verbose logger when configuring an auth-method. This logger will output token claims and information related to how claims are mapped to Nomad identities, and how those identities map to Nomad binding-rules and role/policies.

Testing & Reproduction steps

Create an auth-method and enable the VerboseLogging option. Then start the process of configuring SSO and see the logs.

Links

Fixes GH #16360

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[mismithhisler]

Please feel free to be critical of the log messages I've added, and if you think they are/aren't helpful.

[jrasell]

Looking great, thanks for doing this.

I've added some comments inline which I think would be good to figure out before merging.