[Feature]: API Client cannot create a duplicate route

[davewalter]

Blockers/Dependencies

No response

Background

As a client of the API shim
I want to receive an error when I attempt to create a duplicate route based on its FQDN + context path
So that I am prevented from creating a route if it already exists

Acceptance Criteria

With context path

GIVEN I have an existing route (e.g. foo.example.com/bar )
WHEN I try to make another route with that same host, domain, and context path
THEN receive a 422 error

{
  "errors": [
    {
      "code": 10008,
      "detail": "Route already exists with host 'foo' and path '/bar' for domain 'atom-kitten.capi.land'.",
      "title": "CF-UnprocessableEntity"
    }
  ]
}

Without context path

GIVEN I have an existing route (e.g. foo.example.com )
WHEN I try to make another route with that same host and domain
THEN receive a 422 error

{
  "errors": [
    {
      "code": 10008,
      "detail": "Route already exists with host 'foo' for domain 'atom-kitten.capi.land'.",
      "title": "CF-UnprocessableEntity"
    }
  ]
}

Dev Notes

• Start by implementing this the same way as we do for app names (with leases)
  • We recognize that the direct kubectl apply use case may not have sufficient guards against tampering, but the main API use case remains covered

[kieron-dev]

@davewalter, I have a couple of questions:

1. Does a route need a unique FQDN+path within the space where it is created, or throughout CF - i.e. in the root namespace?
2. How should the associated domain be included in the uniqueness checking? We could use the domain name from the domain resource, but then there is the worry that the domain name could be modified there directly, making the route name stored in the registry out of date. Or we could use the domain's name and namespace as part of the uniqueness check, which relies on the domain name being unique throughout CF.

[tcdowney]

Food for thought: Unlike most resources, Domains in CF can't be updated. I know the CRs can right now, but if we found ways to make them "immutable-ish" that could help with those questions.

https://v3-apidocs.cloudfoundry.org/version/3.115.0/index.html#update-a-domain

[kieron-dev]

It also seems impossible to update host, path and domain on a route via the API. So maybe they should be made immutable too.