feat(oidc): Creation Of New Provider Type Option For Provider Config

[RyanDerr]

Overview

This PR adds a new optional ProviderType field to the OIDC Config struct. The purpose of this option is to allow callers to identify which OIDC provider they are configuring so that provider specific logic can be triggered in cap.

Currently the only initial supported type is Azure, which will enable in the future resolving group overage claims.

Changes

• Creation of a new file provider_type.go within the oidc package which contains the following:
  • ProviderType string type
  • ProviderTypeAzure constant to denote the Azure provider
  • A SupportedProviderType helper function that validates if a given provider type is supported within the library
• Addition of the ProviderType field to the Config struct in addition to the WithProviderType option function that sets ProviderType on a Config during construction.
• Modification of the Config methods:
  • Validate which now rejects and throws an error any non-empty provider type ProviderType supplied that is not currently known and supported.
  • Hash adds the ProviderType in the hash input to be computed, such that the hash is consistent across all config fields.

[louisruch]

LGTM