[TASK] explore creating schema validation for env keys in values.yaml

[hamza-m-masood]

Describe the use case:

Continuation of #2475
The schema is already added for 8.7 chart.
Explore if this schema can be enhanced for validating the env keys in the values.yaml

Describe the enhancement/feature:

For example, this could be implemented by copying the k8s pod env schema using post-rendering after generating the chart and pasting it into the corresponding chart components env for the schema to validate the env keys.

Desired outcome and acceptance tests:

If an incorrect env key is provided then the schema should result in an error.

[falko]

Validation and/or code completion on env vars would be huge given how many things are configured through them, how difficult they are to find in the docs, e.g. derived via naming conventions from other config files, and how spectacular they can fail, e.g. disabling ES exporter and still having some leftover env var.

[jessesimpson36]

Here's the syntax someone could use

                        "extraEnvVars": {
                            "type": "array",
                            "description": "env",
                            "items": {
                                "type": "object",
                                "properties": {
                                    "name": {
                                        "type": "string",
                                        "description": "env",
                                        "enum": ["VALID_OPTION_1", "VALID_OPTION_2"]
                                    },
                                    "value": {
                                        "type": "string",
                                        "description": "env value"
                                    }
                                }
                            }
                        }

And here's the error that would get printed:

> helm template cpt  charts/camunda-platform-8.8                                                               
Error: values don't meet the specifications of the schema(s) in the following chart(s):
camunda-platform:
- elasticsearch.master.extraEnvVars.0.name: elasticsearch.master.extraEnvVars.0.name must be one of the following: "VALID_OPTION_1", "VALID_OPTION_2"

The harder part of this topic is how do you get the list of all valid environment variables that a spring application could accept? and what about java libraries that accept environment variables, but not necessarily using Spring properties, like configuring OpenSearch client env vars. And is the error format above going to be overwhelming to look at with over 200 env vars listed on a single line?

[jessesimpson36]

Helm has a --skip-schema-validation flag. So hypothetically, if we released a 200 variable list and forgot about env var number 201 that isn't accounted for in that list, then a user could then use --skip-schema-validation so that they could add the env var.