Inherit domain and authorization from superclass in Purple::Client

[kalashnikovisme]

Motivation

• Reduce duplication and allow wrapper subclasses to reuse common configuration by falling back to the superclass domain and authorization when not explicitly set on a subclass.

Description

• Make Purple::Client.domain return @domain || inherited_domain so subclasses inherit the domain when unset and add the private helper inherited_domain that calls superclass.domain if available.
• Make Purple::Client.authorization return @authorization || inherited_authorization so subclasses inherit authorization when unset and add the private helper inherited_authorization that calls superclass.authorization if available.
• Add new RSpec tests in spec/purple/client_inheritance_spec.rb that verify inherited domain, inherited authorization, and the ability to override both in a subclass.

Testing

• Added unit tests in spec/purple/client_inheritance_spec.rb (not executed in this environment).
• Attempted to run bundle exec rspec spec/purple/client_inheritance_spec.rb spec/purple/client_spec.rb but the test run failed with bundler: command not found: rspec in the current environment.
• Attempted bundle install to install test dependencies but it failed due to network access to rubygems.org returning HTTP 403 Forbidden, preventing the tests from being executed here.

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Codex Task