Add `CreateAccessKey`, `UpdateAccessKey`, `DeleteAccessKey`, `ListAccessKeys`, and `GetAccessKeyLastUsed` actions for managing user access keys and retrieving their latest usage details.
Generate AWS-style access key IDs and secrets, validate key identifiers and statuses, enforce per-user key quotas, and prevent deleting users that still own access keys. Persist access keys across internal and Vault storage backends with ownership indexing, pagination, and IAM-compatible errors and XML responses.
