Add Teleport to CorpSec index and clarify ownership

Why is this change being made?

Teleport ownership has been in the state of transfer to CorpSec for some time. This MR clarifies the ownership in the handbook as discussed in a recent handoff sync.

The main split of ownership is that CorpSec does not have the technical expertise or staffing to support full technical ownership of this service since it is run in Kubernetes. The agreement was that Foundations would provide maintenance (keeping the lights on) work, but any improvements or changes would run through CorpSec and at that point they can decide if they would like to either invest in building the technical expertise needed, or migrating to a technical area they have more expertise in (such as running on VMs).

This MR seeks to express that split in the handbook.

The other responsibility that was discussed was individual request approvals. This is another area where CorpSec does not have staffing to cover, but has committed to moving forward the automation needed to lower or remove this responsibility from Production Engineering SREs in the Project Zero Console work. This specific example is not highlighted in the MR since it is captured under the category of "improvement".

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
  • Division: If the update affects your division, share the MR in your division Slack channel
  • Company: If the update affects all (or the majority of) GitLab team members, post an update in #whats-happening-at-gitlab linking to this MR
    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

Commits

• Add Teleport to CorpSec index and clarify ownership

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