Is your feature request related to a problem? Please describe.
Currently, multi is only supported for update, patch and remove. But create also has a "multi mode", if the multi: true option is set for a service.

Describe the solution you'd like
Multi should also be available for create, although it is no extra documentation endpoint like the others. It could still be documented for OpenAPI 3 using the oneOf option keyword.

Additional context
Originally requested in #218.