docs: add OTPKI Connector integration guide

[karolhrdina]

Summary

Adds an administrator-facing integration guide for the OTPKI Connector — an ILM Authority Provider v3 connector that fronts the OTPKI backend over Connect-RPC — modelled on the existing EJBCA NG Connector guide.

What's included

• How the connector works — architecture and the two configuration planes (process env vars vs. per-request ILM authority attributes), with a PlantUML issuance sequence diagram
• Deploy — environment-variable reference, Docker, and a hardened Kubernetes example
• Register the connector in ILM
• Create an authority — the OTPKI connection attributes (base/token URL, OAuth2 client credentials, TLS trust, timeouts/retries)
• Create RA profiles — end-entity profile → certificate profile / CA cascade, and login-id strategies
• Certificate lifecycle — issue, renew, register, revoke (with supported reasons), discover, CRL
• Attributes v2 interface (/v2/attributes)
• Constraints and Troubleshooting

Also lists the connector in the available-connectors catalog.

Files

• docs/certificate-key/integration-guides/otpki-connector/integration-guide.md (new)
• docs/certificate-key/integration-guides/otpki-connector/_category_.json (new)
• docs/certificate-key/connectors/available-connectors.md (catalog row)

Verification

• Full docusaurus build passes — MDX compiles and the onBrokenLinks: 'throw' checker passes repo-wide.
• The PlantUML diagram was validated through the repo's render pipeline (marker/normalize/hash).

Content was sourced from the connector on the issue-25 branch (OmniTrustILM/otpki-connector#25, Attributes v2 interface).

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[3keyroman]

This seems to be technical documentation instead of user guidance on how to setup integration with OTPKI, which does not belong here.

The connector is already part of the Helm chart or operator for deployment.

The integration guide should contain description what needs to be configured in OTPKI to make integration happen and test. See other integration guide. This should be removed.

[karolhrdina]

Reworked the guide to focus on the OTPKI-side setup and testing, matching the other integration guides. It now covers: the OAuth2 client the connector authenticates as and the operations it must be allowed to perform; the CA, certificate profile, and end-entity profile to configure in OTPKI (including the API-enrollment and supplied-password requirements the profile must meet); connecting the OTPKI authority in ILM; and testing by issuing a certificate. The connector deployment and internal-API sections are removed, since the connector ships with ILM via the Helm chart / operator.

One open point: the connector repository doesn't document the exact OTPKI admin procedures (they are assumed pre-provisioned), and I couldn't find an OTPKI product-documentation URL to reference. The guide describes what must exist and defers the how-to to "the OTPKI documentation". Is there an OTPKI docs page I should link for those steps?