Add GetEnvVarName() method to parameter types

[Copilot]

Adds a method to retrieve the environment variable name for any parameter, enabling programmatic access to env var names for documentation, help text, and configuration tooling.

Implementation

• Generator template (generate/param_generator.go):

  • Added paramNameToEnvVar() helper: replaces dots with underscores, uppercases, prepends PELICAN_
  • Added GetEnvVarName() method to all param types: StringParam, StringSliceParam, IntParam, BoolParam, DurationParam, ObjectParam

• Generated code (param/parameters.go): Contains method implementations for all parameter instances

• Tests (param/param_test.go): Unit tests and viper integration test

Usage

// Get env var name for any parameter
envVar := param.Cache_Port.GetEnvVarName()
// Returns: "PELICAN_CACHE_PORT"

// Use in help text or documentation
fmt.Printf("Configure via: export %s=8443\n", param.Cache_Port.GetEnvVarName())

// Works with all parameter types
param.Federation_DiscoveryUrl.GetEnvVarName()  // "PELICAN_FEDERATION_DISCOVERYURL"
param.TLSSkipVerify.GetEnvVarName()            // "PELICAN_TLSSKIPVERIFY"

Original prompt

---

This section details on the original issue you should resolve

<issue_title>The param package should provide a getter for environment variables</issue_title>
<issue_description>Given a param like param.SomeThing, we should provide a method on the param that returns a string representing that param's Pelicanized environment variable, e.g.

envVarName := param.Some_Thing.GetEnvVarName()
// envVarName holds PELICAN_SOME_THING
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes The param package should provide a getter for environment variables #2833

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