Add solution design document for ingress

[bnshr]

This PR adds descriptive documentation about the codebase and key design decisions for the ingress solution, providing stakeholders with an overview of the ingress commatrix approach.

Assisted-by: Cursor AI Editor

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: bnshr
Once this PR has been reviewed and has the lgtm label, please assign schseba 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

[bnshr]

/retest

[openshift-ci]

@bnshr: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/commatrix-e2e-tests	ab46121	link	true	/test commatrix-e2e-tests
ci/prow/commatrix-e2e-tests-1of2	ab46121	link	true	/test commatrix-e2e-tests-1of2
ci/prow/commatrix-e2e-tests-2of2	ab46121	link	true	/test commatrix-e2e-tests-2of2

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.