🐞[BUG] Editing "sendTo" BPN changes "createdBy" BPN

[ds-crehm]

Description

When editing a notification and changing the receiver BPN, that data remains unchanged while the "createdBy" BPN is set to the changed value. EDIT: CreatedBy BPN always changes regardless of what was edited, which means editing and then sending notifications is not possible currently.

Current behaviour

When I look at a notification:

And I want to change the "Sent to BPN" value and go to the edit mode:

And then save it, the "Sent to BPN" value stays the same, while the "Created by BPN" is changed:

(In the backend, the "createdBy" value changes, while the "sendTo" value remains the same.)

Expected behavior

When I change the receiver BPN, I expect the "Sent to BPN" to be changed instead of the "Created by BPN". The "Created by BPN" must never be changed in the notification.

Additionally, the error pop-up message when approving this kind of notification should be more descriptive, so that the user knows what the problem is and that it's not possible to send notifications with a different senderBPN. Then he can close this notification and create a new one.

Steps to reproduce the Bug

1. Create a notification
2. Edit the notification and change the BPN value
3. Go to detail view of the notification to view the changes

[ds-crehm]

Whenever I receive a notification the "createdBy" BPN is always my own, which is technically correct but it's confusing. Either it should be the one who initially created the notification or it could be renamed to "sentBy" and then have the correct BPN or it can be removed if it always contains the own BPN (then it has no use).

[ds-lcapellino]

With the PR: #1327, the expected behavior was verified on dev environment.
Step1: Created alert

Step2: change receiver BPN

Step3: see new receiver BPN

[ds-crehm]

Tested successfully on E2E:
I create the following notification with a wrong BPN and I can't send it:

I edit the nontification to use the correct BPN:

Now I can send it:

Ready for review.