[FSSDK-11837] legacy api adjustment with key null support in decide

[junaed-optimizely]

Summary

This pull request adds a new validation for null flag keys in the decision logic, ensuring that passing a null flag key to the Decide method returns a proper error decision. It also introduces a corresponding unit test to verify this behavior.

Error handling improvements:

• Added a check in Optimizely.cs to return an error decision if the flag key passed to Decide is null, using a specific error message (FLAG_KEY_INVALID).

Testing enhancements:

• Added a new test, DecideNullFlagKey, in OptimizelyUserContextTest.cs to verify that passing a null flag key returns the expected error decision.

Issues

FSSDK-11837

[Copilot]

Pull Request Overview

This pull request improves error handling in the Optimizely SDK by adding validation for null flag keys in the Decide method. When a null flag key is passed, the method now returns a proper error decision with a specific error message instead of potentially causing downstream issues.

• Added null check validation in the Decide method to return an error decision for null flag keys
• Added unit test to verify the new null flag key validation behavior

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
OptimizelySDK/Optimizely.cs	Added null check for flag key parameter in Decide method with proper error handling
OptimizelySDK.Tests/OptimizelyUserContextTest.cs	Added unit test to verify null flag key returns expected error decision

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[mikechu-optimizely]

I agree with the check for key equals null check and the supporting unit test.