JSD agents / JSD customer accounts / Jira users cannot be created: all directory read only (from in-product invite / REST api)

Summary

JSD customer / agents + Jira users cannot be created with error "all directory read only", when created from in-product invite + REST APIs. Problem was first observed in JSD Widget and public REST API, but later discovered to affect other parts of JSD / Jira:
• JSD anonymous portal ticket creation (if email address is a customer account that doesn’t exist and needs user creation)
• JSD email ticket creation (if email address is a customer account that doesn’t exist and needs user creation)
• JSD widget ticket creation (if email address is a customer account that doesn’t exist and needs user creation)
• JSD customer portal signup (customer account creation)
• JSD invite customer (customer account creation)
• JSD invite agent
• JSD public api for creating customer accounts
• Jira REST API user creation

Status Page: https://status.atlassian.com/incidents/9r351r9v5cdw