Adds `TagOpenIDConnectProvider`, `UntagOpenIDConnectProvider` and `ListOpenIDConnectProviderTags` to the standalone IAM service, backed by both the internal and Vault storers. They follow the user and role tagging actions in most respects — the tag action merges into the provider's existing tags and rejects a repeated key, untag removal is idempotent, and the tag listing is sorted by key and paginated, with the per-request member count and the per-provider tag total enforced as separate quotas so replacing a tag on a provider already at the 50-tag cap still succeeds — but differ in the one respect IAM itself draws: OIDC provider tag keys are compared exactly, not case-insensitively. On a provider `env` and `ENV` are two independent tags, both may be supplied in a single request, only a byte-identical repeat is a duplicate (reported without the "Tag keys are case insensitive" note the user and role actions carry), and untagging `env` leaves `ENV` in place.
That distinction is now carried by `iamutil.TagKeyCase`, which `ParseTags` uses for duplicate detection and which `mergeTags`, `removeTags` and the tag listing's marker lookup use for key matching. `CreateOpenIDConnectProvider` moves onto the exact comparison too, so a provider created with case-differing tag keys keeps both.
All three actions are authorized against the target provider's ARN, so `aws:ResourceTag/<key>` reads the provider's own tags, and the tag and untag actions populate `aws:RequestTag/<key>` and `aws:TagKeys` respectively, so a tag-scoped policy Condition governs which tags a caller may set or remove. All three report a missing provider with the wording `DeleteOpenIDConnectProvider` uses rather than the one `GetOpenIDConnectProvider` uses, which is why the Vault provider read now takes the not-found error its calling action reports.
The WebGUI gains a Tags section in the OIDC provider manage view, replacing the read-only tag row, and the shared tag editor gains a case-sensitive mode that changes its duplicate-key check, its diffing of an edited set into an untag and tag pair, and the wording of its guidance.
Add support for `CreateOpenIDConnectProvider`, `GetOpenIDConnectProvider`, `ListOpenIDConnectProviders`, `DeleteOpenIDConnectProvider`, `AddClientIDToOpenIDConnectProvider`, `RemoveClientIDFromOpenIDConnectProvider`, and `UpdateOpenIDConnectProviderThumbprint` on both the internal and Vault storage backends, rounding out the standalone IAM service with the same OIDC identity provider management AWS IAM exposes.
CreateOpenIDConnectProvider validates the issuer URL, enforces the client ID and per-provider client ID list limits, and accepts an optional ThumbprintList. When the caller omits ThumbprintList, the provider auto-fetches the thumbprint by opening an outbound TLS connection to the issuer URL and hashing its top-level CA certificate, matching real AWS behavior. This auto-fetch is configurable: it can be turned off with the `--disable-oidc-thumbprint-autofetch` CLI flag (or the `VGW_IAM_DISABLE_OIDC_THUMBPRINT_AUTOFETCH` environment variable) for restricted or air-gapped deployments where the IAM server shouldn't make outbound connections, in which case an omitted ThumbprintList is rejected instead. AddClientIDToOpenIDConnectProvider and RemoveClientIDFromOpenIDConnectProvider manage a provider's client ID list, and UpdateOpenIDConnectProviderThumbprint replaces its thumbprint list, all with the same length and format validation applied at creation time.
Provider ARNs are derived from the issuer URL, and GetOpenIDConnectProvider and DeleteOpenIDConnectProvider resolve providers by ARN, returning NoSuchEntity when a provider doesn't exist. ListOpenIDConnectProviders returns the full set of stored providers. These actions are wired into the IAM API router and given their own XML response types under iamapi/types, with a new iamapi/internal/iamutil package handling URL validation, thumbprint fetching and normalization, and ARN construction shared across the controller methods.
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