fix: return full status object from the info endpoint

[LucasRoesler]

Description

Ensure that all fields of the FunctionStatus are populated based on
the function Deployment. In particular, this change ensures that the
env variables, constrains, and the read-only root filesystem values are
populated correctly.

Found while updating the faas-cli, see openfaas/faas-cli#915

Motivation and Context

• I have raised an issue to propose this change (required)

Resolves #922

How Has This Been Tested?

The extended unit tests fully cover the new code.

As stated in the PR title, this adds missing fields to the function info endpoint: /system/function/{function_name}

Without this change, the endpoint misses values like readOnlyFilesystem

$ curl -s http://localhost:8080/system/function/echo | jq
{
  "name": "echo",
  "image": "ghcr.io/lucasroesler/echo:latest",
  "namespace": "openfaas-fn",
  "labels": {
    "faas_function": "echo",
    "uid": "351420882"
  },
  "annotations": {
    "foo": "bar",
    "prometheus.io.scrape": "false"
  },
  "replicas": 1,
  "availableReplicas": 1,
  "createdAt": "2022-06-11T14:40:28Z"
}

With this change

$ curl -s http://localhost:8080/system/function/echo | jq
{
  "name": "echo",
  "image": "ghcr.io/lucasroesler/echo:latest",
  "namespace": "openfaas-fn",
  "labels": {
    "faas_function": "echo",
    "uid": "351420882"
  },
  "annotations": {
    "foo": "bar",
    "prometheus.io.scrape": "false"
  },
  "readOnlyRootFilesystem": true,
  "replicas": 1,
  "availableReplicas": 1,
  "createdAt": "2022-06-11T14:40:28Z"
}

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.

[alexellis]

Is there a chance that the Istio sidecar could take position 0?

[alexellis]

Could it be indexed upon some kind of property or name in a range loop?

[alexellis]

Could SecurityContext ever be nil?

[LucasRoesler]

Yes, it can be nil, but this is checked immediately on the next line.

[LucasRoesler]

regarding the position of the container:

Both the controller and the handler put the labels on the Pod, but not the container. We can use the container Name though, it will equal the deployment.Name.

As a side note, it would be really nice if we could refactor the an unify the generation of the Deployment, the function Factory doesn't actually generate it, both the controller and the handler have different code for the construction of the Deployment

[LucasRoesler]

@alexellis i have updated the code and replaced all instances of Containers[0] with a proper FunctionContainer() implementation that finds the correct index and container spec.

[alexellis]

Thank you

[alexellis]

Can you remind me which endpoint this is for by showing an example of before/after with curl under How Has This Been Tested??

[LucasRoesler]

@alexellis I have updated the PR description with the curl examples. As stated in the PR title this impacts the function info endpoint: /system/function/{function_name}