Fix: Environment variable access logic for config

[this-Aditya]

The config values are only read from environment variables if they are null. This doesn’t prioritize environment variables above local config values. The logic now uses the radar-jersey helper functions to prioritize environment variables over local configuration, checking the environment variables every time.

[Copilot]

Pull request overview

This pull request refactors the environment variable handling in configuration classes to properly prioritize environment variables over local configuration values. The previous implementation only read from environment variables when config values were null, which didn't allow environment variables to override non-null local config values.

Changes:

• Changed configuration properties from mutable (var) to immutable (val) to support functional-style configuration updates
• Replaced checkEnvironmentVars() methods with withEnv() methods using radar-jersey helper functions (copyEnv, copyOnChange)
• Modified the configuration loading flow in Main.kt to call withEnv() during initialization rather than checking environment variables after validation

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
S3StoragePathConfig.kt	Converts properties to immutable and adds withEnv() method to apply environment variable for path prefix
S3StorageConfig.kt	Converts properties to immutable and adds withEnv() method to apply environment variables for S3 configuration (URL, access key, secret key, bucket name, region, and nested path config)
GatewayConfig.kt	Replaces checkEnvironmentVars() with withEnv() method to propagate environment variable handling to S3 storage configuration
Main.kt	Integrates withEnv() into the configuration loading chain after withDefaults() and removes the separate checkEnvironmentVars() call

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[mpgxvii]

LGTM! (Just a minor comment)