feat: added postman collection for integration test

[tom-rm-meyer-ISST]

Description

Added Postman collection to prepare and run integration tests based on non-demo setup puris instances.

It creates a setup of a partner and customer that refer to the same material from the other perspective:

• The customer has the material and a material stock
• The supplier has the product and a product stock
• Both partners know each other and each other's EDC
• The setup is ready to trigger the update from customer to supplier

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

[tom-rm-meyer-ISST]

@eschrewe please review. I changed the following:

• added a listing of test data in local/postman/README.md.
• streamlined variables to be consistent to supplier / customer (no mixture with consumer / provider)
• updated application properties to names used in README.md -> will need further update in others

[eschrewe]

Well done, I like it very much :)
My remarks are concerning only some minor issues

[eschrewe]

Thanks a lot, great effort!
Only a small handful of things I noticed, see the new comments

[mhellmeier]

Okay for me. Even if there are >1000 LOC, the majority of lines are based on a JSON export of the Postman collection. Therefore, merging is fine for me.