[Backend] Reject notifications to the own BPN

[ds-crehm]

As user,
I want that the application rejects notifications that I send to my own BPN,
so that I won't cause problems in the system.

Hints / Details

When a user sends a notification that is adressed to his own BPN, the system must reject that notification. Otherwise the database will have problems with this scenario and might break.

Acceptance Criteria

• When receiving a notification, Trace-X must verify if the BPN is different than the BPN of the currently running instance.
• If the BPN is identical, the notification must be rejected with the error 'Bad Request'
• validate that it doesnt work in FE to use own BPN

Out of Scope

-Error Message enrichment will be provided in #787

[ds-crehm]

Frontend implementation works on E2E-A:

Alert can not be created with own BPN.

Does not work on E2E-B. When typing BPNL00000003CNKC there, it's not rejected. The notification can be created. After approving it, an error is thrown "Alert failed to send, please try again."

In the backend directly, I can create notification with the own BPN as receiver. After approving them, I receive the error 503:

And in the notification, following error is saved:

The request response and the error message are not very descriptive. Please check if that can be improved, as it was part of the acceptance criteria to handle it as 400 Bad request.

(If the frontend verification works correctly, the error message is not as important, as the user should never have the possibility to create such a notification in the first place.)

[ds-crehm]

Works properly now for E2E-B as well. (Rejected when choosing own BPN)

Now the backend also throws a 400 Bad request with a proper error message:

Verification is implemented for creating and editing notifications. Both processes were tested and work as expected.

Ready for review.

[mkanal]

PO acceptance in behalf of @jzbmw. Works as intended.