"Date Received" for contributions no longer mandatory, also breaks financial transactions

This issue affects at least versions >5.3 - I was able to reproduce it on the current master as well. I would consider it a rather critical bug but maybe there is more to it (new, not fully finished feature)?

Description

The contribution field "Date Received" used to be mandatory which imho had several good and important reasons. It is now possible to create a contribution without a date both via the UI and the Rest API.

Having a contribution without a date messes up views, reports and any function based on the contribution date such as receipts or invoices.

Also it creates a financial transaction without a date which cannot be good. In the UI, financial transactions still require a date.

How to reproduce

Create a new contribution via the UI and delete the date and time in the field "Date Received". Contribution date and financial transaction date will be empty.