Hardcoded System.getenv() calls prevent programmatic configuration of parameters #1022
Description
The Google ADK currently relies strictly on System.getenv() to read critical configuration parameters, specifically GOOGLE_GENAI_USE_VERTEXAI, GOOGLE_CLOUD_PROJECT, and GOOGLE_CLOUD_LOCATION.
This creates a significant architectural friction point for modern Java applications, such as Spring Boot on Java 17+. In these environments, configurations are managed internally via files like application.yaml rather than static OS-level environment variables. Because Java's System.getenv() reads an immutable OS map, we are completely blocked from programmatically injecting or wiring these values from our application's configuration at runtime.
This forces developers to rely on external CI/CD deployment wrappers or unsafe JVM reflection hacks just to pass standard configuration values into the SDK.