post:
  operationId: generateStaffUsername
  summary: Generate a preview username for a staff account
  description: |
    Permission: **OWNER only**

    - Returns a username preview in format `nova.{initial}{lastname}.{XX}` (lowercase).
    - Does **not** persist to DB — uniqueness is only guaranteed at `CreateStaffUser` time.
    - Call before submitting `CreateStaffUser`. Client may call again ("Re-generate") to get a new value.
  tags: [staffManagement]
  security:
    - bearerAuth: []
  requestBody:
    required: true
    content:
      application/json:
        schema:
          $ref: "../../components.yaml#/components/schemas/GenerateStaffUsernameRequest"
        example:
          first_name: "Jane"
          last_name: "Doe"
  responses:
    "200":
      description: Generated username preview — DTO returned directly
      content:
        application/json:
          schema:
            $ref: "../../components.yaml#/components/schemas/GenerateStaffUsernameResponse"
          example:
            username: "nova.jdoe.43"
    "400":
      $ref: "../../components.yaml#/components/responses/Failure"