USHIFT-2245: Add router namespace ownership enhancement

enhancements/microshift/microshift-route-admission-policy.md

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+---
+title: microshift-route-admission-policy
+authors:
+  - "@pacevedom"
+reviewers:
+  - "@eslutsky"
+  - "@copejon"
+  - "@ggiguash"
+  - "@pmtk"
+  - "@pliurh"
+  - "@jerpeter1"
+  - "@Miciah"
+approvers:
+  - "@dhellmann"
+api-approvers:
+  - None
+creation-date: 2024-01-30
+last-updated: 2024-02-01
+tracking-link:
+  - https://issues.redhat.com/browse/OCPSTRAT-1067
+see-also:
+  - "/enhancements/ingress/openshift-route-admission-policy.md"
+---
+
+# MicroShift route admission policy
+## Summary
+OpenShift defaults to not allow routes in multiple namespaces use the same
+hostname, and MicroShift inherits that default.
+
+Ever since OpenShift 4 this has been possible to configure, and MicroShift
+should allow that too to accommodate additional use cases.
+
+## Motivation
+Users who compose applications from multiple sources may deploy those to
+different namespaces, albeit want to expose them using the same hostname and
+different path.
+
+### User Stories
+As a MicroShift admin, I want to configure MicroShift to support combining
+routes from multiple namespaces.
+
+### Goals
+- Allow the use of the same host in routes from different namespaces.
+
+### Non-Goals
+N/A
+
+## Proposal
+The proposal follows all the changes that were done in the original
+[enhancement](https://github.com/openshift/enhancements/blob/master/enhancements/ingress/openshift-route-admission-policy.md).
+
+This includes the exposure of a new configuration option to pass on to the
+router to allow cross-namespace host routes.
+
+MicroShift will default to disable the namespace ownership checks, contrary to
+OpenShift. MicroShift is not meant to be multi-tenant and hold several
+unrelated applications that need protection between them.
+
+MicroShift is also focused on single-node deployments, and runs without an
+external load balancer and in environments without access to deep DNS
+integration. The primary means of accessing the apps on the MicroShift host
+will be the single hostname of that host.
+
+### Workflow Description
+
+### API Extensions
+To allow configuring the router a new option is exposed through the MicroShift
+configuration file:
+```yaml
+ingress:
+  routerAdmissionPolicy:
+    namespaceOwnership: <Strict|InterNamespaceAllowed> # Defaults to InterNamespaceAllowed.
+```
+
+In order to keep configuration as close to OpenShift, the option and its values
+are the same.
+
+When set to `Strict` the router will not allow routes in different namespaces
+to claim the same host.
+When set to `InterNamespaceAllowed` the router will allow routes in different
+namespaces to claim different paths of the same host. This is the default
+value, as MicroShift's typical use cases are not multi-tenant and this is the
+most flexible value.
+
+### Topology Considerations
+#### Hypershift / Hosted Control Planes
+N/A
+
+#### Standalone Clusters
+N/A
+
+#### Single-node Deployments or MicroShift
+This enhancement is intended solely for MicroShift
+
+### Implementation Details/Notes/Constraints
+N/A
+
+### Risks and Mitigations
+N/A
+
+### Drawbacks
+N/A
+
+## Design Details
+See original [enhancement](https://github.com/openshift/enhancements/enhancements/ingress/openshift-route-admission-policy.md)
+for more details.
+
+## Test Plan
+Same as original [enhancement](https://github.com/openshift/enhancements/enhancements/ingress/openshift-route-admission-policy.md).
+These tests will be included as part of the automatic tests in CI.
+
+## Graduation Criteria
+### Dev Preview -> Tech Preview
+- Ability to utilize the enhancement end to end
+- End user documentation, relative API stability
+- Sufficient test coverage
+- Gather feedback from users rather than just developers
+
+### Tech Preview -> GA
+- Sufficient time for feedback
+- Available by default
+- User facing documentation created
+
+### Removing a deprecated feature
+N/A
+
+## Upgrade / Downgrade Strategy
+N/A
+
+## Version Skew Strategy
+N/A
+
+## Operational Aspects of API Extensions
+N/A
+
+### Failure Modes
+N/A
+
+## Support Procedures
+N/A
+
+## Implementation History
+N/A
+
+## Alternatives
+N/A