feature: support for checking against HTTP status code

[MrPeacockNLB]

Description

The integrated healthcheck should be able to check a HTTP a status code.

E.g. we are deploying an K3D cluster inside out workspace. The healthcheck is already green but user facing a 404 error page from kubernetes as the app is not up and running. Checking against a status code 200 should solve this.

Setting a explicit statuscode should change the default checking.

resource "coder_app" "code-server" {
  agent_id     = coder_agent.dev.id
  slug         = "code-server"
  display_name = "VS Code"
  icon         = "${data.coder_workspace.me.access_url}/icon/code.svg"
  url          = "http://localhost:13337"
  share        = "owner"
  subdomain    = false
  healthcheck {
    url       = "http://localhost:13337/healthz"
    interval  = 5
    threshold = 6
    statuscode = 200
  }
}

Expected Behavior

Button should be enabled when application is ready and not when kubernetes cluster has started. If a statuscode 200 is set then the button gets enabled when the application is ready.

Actual Behavior

As soon kubernetes cluster is ready the healtcheck is green and buttons are enabled