Dup as_json options if frozen for Rails 8 compatibility

[chrisrbnelson]

Rails 8.0 introduced a change which freezes the options hash in ActiveSupport's .as_json method.

quickbooks-ruby overrides this method to add some ROXML exclusions, and this now breaks after updating to Rails 8.

# e.g. from calling `Quickbooks::Service::TaxCode.new(...).fetch_by_id(...).as_json`
FrozenError:
  can't modify frozen Hash: {except: ["roxml_references"]}
/cache/gems/ruby/3.4.0/gems/quickbooks-ruby-2.0.5/lib/quickbooks/model/base_model.rb:35:in 'Quickbooks::Model::BaseModel#as_json'
/cache/gems/ruby/3.4.0/gems/activesupport-8.0.1/lib/active_support/core_ext/object/json.rb:192:in 'block in Hash#as_json'
/cache/gems/ruby/3.4.0/gems/activesupport-8.0.1/lib/active_support/core_ext/object/json.rb:192:in 'Hash#each'
/cache/gems/ruby/3.4.0/gems/activesupport-8.0.1/lib/active_support/core_ext/object/json.rb:192:in 'Hash#as_json'
/cache/gems/ruby/3.4.0/gems/activesupport-8.0.1/lib/active_support/core_ext/object/json.rb:63:in 'Object#as_json'
/cache/gems/ruby/3.4.0/gems/quickbooks-ruby-2.0.5/lib/quickbooks/model/base_model.rb:36:in 'Quickbooks::Model::BaseModel#as_json'

The change also broke some other packages which do similar things.

This PR adds a check to dup the hash if it's frozen so it can be modified which avoids the issue.