Proposed manifest change

Description

This MR relates to Robotnik Issue #17. The goal is to add a new top level key named partner_advocate, this key is intended to allow CHT members to be assigned as advocates to vendor owned repositories, without being assigned issues (as the maintainers are). This gives vendors a CHT member to reach out to, for more info please see the discussion in the issue linked above.

The partner_advocates key is nearly exactly the same as maintainers, the primary difference are:

• The lack of a cht_member value, at this time partner_advocates can only be filled by CHT members.
• The partner_advocates key unlike maintainers is also not required.
• partner_advocates also will not be added as assignees to issues automatically.

Risk

Risk should be minimal, the only change being made is to the manifest schema, no current keys are being changed only one new key will be added. Complexity overall is very low.

Rollback Plan

Rolling back the schema should resolve any issues that may arise, but if pipelines fail due to the schema validation being incorrect they will need to be re-ran.

Testing

Tests have been added. Below is a sample of what an updated manifest would look like.

---
apiVersion: v1

name: "opensource/amundsen/frontend"

tags:
- "4.2.0"
- "latest"

args:
  BASE_IMAGE: "opensource/python/python37"
  BASE_TAG: "3.7"

labels:
  org.opencontainers.image.title: "Amundsen Frontend"
  org.opencontainers.image.description: "Google search for data."
  org.opencontainers.image.licenses: "Apache-2.0"
  org.opencontainers.image.url: "https://github.com/amundsen-io/amundsen/tree/main/frontend"
  org.opencontainers.image.vendor: "amundsen-io"
  org.opencontainers.image.version: "4.2.0"
  mil.dso.ironbank.image.keywords: "frontend,ui,flask,data"
  mil.dso.ironbank.image.type: "opensource"
  mil.dso.ironbank.product.name: "frontend"

resources:
- tag: amundsendev/amundsen-frontend:4.2.0
  url: docker://docker.io/amundsendev/amundsen-frontend@sha256:720d03b243cd40ad0c1d364ef03e51dcd4ae67928bbf6875865a08ca10483300

maintainers:
  - email: "mlindsey@vivsoft.io"
    name: "Marquis Lindsey"
    username: "mlindsey9106"
    cht_member: True

partner_advocates:
  - name: "Jacob Hanafin"
    username: "jhanafin"

shamelessly stolen from a real repo.