[sampleapp] Add `insert` messaging for all `Relation`s of all defined `Dactor`s in the sample application

[srfc]

Issue

[sampleapp] Add insert messaging for all Relations of all defined Dactors in the sample application.

Problem Description

• there is currently no way to fill one of our defined Dactors with content
• these Dactors have to provide messaging and logic to allow inserting new values into their relations from outside the Dactor itself

Supporting Information

n/a