feat: demand and capacity notification improvements

[eschrewe]

Description

• fixed/improved DemandAndCapacitySammMapper:
• now properly distinguishes between Samms that came from a supplier or a customer, when identifying the affected materials
• now using customermaterialnumber / suppliermaterialnumber fields in the samm/json payload
• added unit tests for samm mapper
• solves Add tests for serialization of SAMM models #465

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files
• If helm chart has been changed, the chart version has been bumped to either next major, minor or patch level (compared to released chart).

[tom-rm-meyer-ISST]

Please test correct mapping of all fields. Beside that you solved #486 ! Thanks a lot :)

[tom-rm-meyer-ISST]

Currently only serialization has been checked with regard to material mapping. Please also add mapping assertions for deserialization.

[tom-rm-meyer-ISST]

LGTM, thanks for the update!