Hi Bob
For inbound IDocs into SAP, they are normally sent as an RFC call to the remote-enabled function module IDOC_INBOUND_ASYNCHRONOUS. This will be the entry point to the SAP backend system.
Posting of inbound IDocs can generally be simplified into two parts:-
i) creation of IDoc content in the database
ii) processing of IDoc in application
It looks like you want to decouple these two parts, this can be easily achieved by setting the processing option to "Background" in the corresponding partner profile. With this option, at the first step, the IDoc will be created and will be in status 64. It will not be sent for further processing. You will then have to schedule a background job with program RBPAPP01 to process IDocs that are already in status 64. It will call the relevant function module based on the configured process code in the partner profile, and eventually the IDoc will be in status 53 (success) or 51 (error.)
With this approach, for the first step, you can provide a user ID with limited authorization for use by the Boomi tool. For the second step, you can assign a different batch user ID that will actually post the SAP documents.
The following Wiki has a lot of useful links to IDoc related stuff.
ALE and IDocs - ABAP Development - SCN Wiki
Rgds
Eng Swee