feat: add external_id support for organization create/update operations

[basbz]

Add external_id parameter support to create and update operations:

• WorkOS.Organizations.create_organization/1,2 — accepts :external_id in opts
• WorkOS.Organizations.update_organization/2,3 — accepts :external_id in opts

This is a follow-up to #83 which added external_id to the structs and added lookup-by-external-id endpoints. With this PR, the SDK fully supports the external_id field across all CRUD operations for Organizations.dd

[greptile-apps]

Greptile Overview

Greptile Summary

This PR completes the external_id support for Organizations by adding the parameter to create and update operations. The implementation follows the existing codebase patterns and complements PR #83 which added the struct field and lookup-by-external-id endpoints.

• Added external_id parameter to create_organization/1,2 and update_organization/2,3
• Updated documentation to describe the new parameter
• Added comprehensive tests validating the new functionality
• Updated mock client to include external_id in responses

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The changes are straightforward parameter additions that follow existing patterns in the codebase. The implementation is consistent with how other optional parameters are handled, includes proper documentation, and has comprehensive test coverage.
• No files require special attention

Important Files Changed

Filename	Overview
lib/workos/organizations.ex	Added external_id parameter to create and update operations with proper documentation
test/support/organizations_client_mock.ex	Updated mock responses to include external_id field for create and update operations
test/workos/organizations_test.exs	Added comprehensive tests for external_id support in create and update operations

[greptile-apps]

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[gjtorikian]

thank you~