Support structured config

[ljtfreitas]

Context

Currently structured configs are not supported properly by Pulumi k8s operator.

As Pulumi programs can be configured using yaml files, it looks fair to be able to configure a structured, complex config using the Stack CRD as well.

Proposed changes

This PR proposes two approaches to support structured config:

makes the config field support a JSON as value

It could be useful to keep compatibility with older versions. Declaring the config field as a map[string]apiextensionsv1.JSON, existing support to inline fields keeps working (as aws:region: whatever) and expanding the config to a more complex object also works.

To make this work with Pulumi Automation API, in case the value is a json, the same rules used by Pulumi CLI to handle structured configs are applied. The implementation flattens all object keys to generate Pulumi-CLI compatible key names. For example:

config:
  my-key: my-value
  my-list:
    - a
    - b
    - c
  aws:region: us-east-1
  aws:assumeRole:
     roleArn: my-role-arn
     sessionName: my-assumed-session-name

it will generate these config keys/values:

my-key: my-value
my-list[0]: a
my-list[1]: b
my-list[2]: c
aws:region: us-east-1
aws:assumeRole.roleArn: my-role-arn
aws:assumeRole.sessionName: my-assumed-session-name

and all those keys are send through Automation API as Path: true

adds a new field configRefs

adds to CRD a new field called configRefs, that works in a similar way that EnvRefs or SecretRefs, adding two new possible values: configmap and structured

configmap adds support to read a K8s ConfigMap and get a specific key to use as a config value structured is a JSON value that can be used to pass a structured configuration, following the same previous pattern from the config field.

integration tests

I was not able to make the tests pass in my local environment but right now it's just an initial implementation proposal. I can keep working on that if you people think is worth it.

Related issues (optional)

https://github.com/pulumi/pulumi-kubernetes-operator/issues/258