Bug: `create_organization_membership` uses incorrect API endpoint (singular instead of plural)

[max-zheng]

Description

The CreateOrganizationMembership operation in src/user_management/operations/create_organization_membership.rs hits /user_management/organization_membership (singular), but the WorkOS API endpoint is /user_management/organization_memberships (plural).

https://github.com/RustForWeb/workos/blob/main/src/user_management/operations/create_organization_membership.rs#L79

let url = self
    .workos
    .base_url()
    .join("/user_management/organization_membership")?;  // should be /organization_memberships

Expected

POST /user_management/organization_memberships

Actual

POST /user_management/organization_membership

Reference

WorkOS Docs: Create an organization membership

The docs show the endpoint as /user_management/organization_memberships (plural).

Impact

Calls to create_organization_membership silently fail (likely 404), causing users to end up with organizations but no memberships.