fix: add missing configuration accessors for api keys

[duongvanlong]

Description

fix: add missing configuration accessors for api keys

Details

Motivation

Fixes NoMethodError when configuring organization_api_key and rest_api_key. These keys are required for authentication but were missing from the Configuration class.

Scope

• Add attr_accessor for organization_api_key and rest_api_key in configuration.rb
• Add specs to verify these keys can be configured

Testing

Manual testing

• add specs for new attr
• include gem in local repo and add config

Checklist

Overview

• [ x ] I have filled out all REQUIRED sections above
• [ x ] PR does one thing
  • If it is hard to explain how any codes changes are related to each other then it most likely needs to be more than one PR
• [x ] Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• [ x] I have personally tested this on my device, or explained why that is not possible

Final pass

• [ x] Code is as readable as possible.
  • Simplify with less code, followed by splitting up code into well named functions and variables, followed by adding comments to the code.
• [ x] I have reviewed this PR myself, ensuring it meets each checklist item
  • WIP (Work In Progress) is ok, but explain what is still in progress and what you would like feedback on. Start the PR title with "WIP" to indicate this.