Consider support for user specified interaction models on creation of new members

[jamsden]

When creating a new LDPC member, the new member in the POST entity request body might be an LDPC. The entity request body could include all the information needed to specify the interaction model, but the user could override the interaction model details using a Link header.

If this is optional, then it might not be worth implementing. The reason is that it's probably a better practice to have the resource explicitly define the interaction model instead of putting that information in HTTP headers. This is temporary information that represents significant control coupling and may not be a good practice.