OAPE-94: Update API doc for route externalCertificate

[chiragkyal]

Update API godoc to document that manual intervention is required for using .spec.tls.externalCertificate.

https://issues.redhat.com/browse/OAPE-94

[openshift-ci-robot]

@chiragkyal: This pull request references OAPE-94 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.19.0" version, but no target version was set.

In response to this:

Update API godoc to document that manual intervention is required for using .spec.tls.externalCertificate.

https://issues.redhat.com/browse/OAPE-94

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

[openshift-ci]

Hello @chiragkyal! Some important instructions when contributing to openshift/api:
API design plays an important part in the user experience of OpenShift and as such API PRs are subject to a high level of scrutiny to ensure they follow our best practices. If you haven't already done so, please review the OpenShift API Conventions and ensure that your proposed changes are compliant. Following these conventions will help expedite the api review process for your PR.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: chiragkyal
Once this PR has been reviewed and has the lgtm label, please assign bparees for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[chiragkyal]

/cc @Miciah @alebedev87

[openshift-ci]

@chiragkyal: all tests passed!

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[chiragkyal]

/assign @JoelSpeed

[JoelSpeed]

Will let more local SMEs review the text update, ping me when you need an approve label