## What this PR does / why we need it:
In https://github.com/kubernetes/ingress-nginx/issues/5651 there was a
request to throw an error when there are two ingresses defining the same
host and path, which was implemented as part of the validation webhook.
Despite of this there are clear rules on the ingress controller that
describes what the controller would do in [such situation (the oldest
rule wins)](https://github.com/kubernetes/ingress-nginx/blob/main/docs/how-it-works.md?plain=1#L27)
Some users are relying on this validation behaviour to prevent
misconfigurations, but there are use cases where allowing it, maybe
temporarily, is helpful. Those use cases includes:
- Splitting large ingresses objects in smaller ones https://github.com/kubernetes/ingress-nginx/issues/10820
- Moving ingress objects between namespaces without downtime (like when you transfer an ingress from team A that owns namespace A to team B that owns namespace B) https://github.com/kubernetes/ingress-nginx/issues/10090
<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [X] New feature (non-breaking change which adds functionality)
- [ ] CVE Report (Scanner found CVE and adding report)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [ ] Documentation only
## Which issue/s this PR fixes
It might help with #10820
<!--- Please describe in detail how you tested your changes. -->
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## How Has This Been Tested?
building an image and testing it in a local cluster, will update later
with some real life scenarios
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## Checklist:
- [X] My change requires a change to the documentation.
- [ ] I have updated the documentation accordingly.
- [X] I've read the [CONTRIBUTION](https://github.com/kubernetes/ingress-nginx/blob/main/CONTRIBUTING.md) guide
- [X] I have added unit and/or e2e tests to cover my changes.
- [X] All new and existing tests passed.
Change-Id: I9d4124d1c36876b06d63100cd10988eaf2f41db9
* Add validation to all annotations
* Add annotation validation for fcgi
* Fix reviews and fcgi e2e
* Add flag to disable cross namespace validation
* Add risk, flag for validation, tests
* Add missing formating
* Enable validation by default on tests
* Test validation flag
* remove ajp from list
* Finalize validation changes
* Add validations to CI
* Update helm docs
* Fix code review
* Use a better name for annotation risk
* exclude creation and exporting of socket metrics via flag
* make exclude metric naming more consistent
* fix connect time metric update
* add documentation
* e2e test
* improve creation of metric mapping
