[TASK] Enforce setting up MFA

With #93526, multi-factor authentication was
introduced to TYPO3. This came with several
configuration options, such as the possibility
to require MFA for specific users and user
groups. Previously, the only result of this
option was a warning, displayed in the MFA
configuration module. Obviously, this did not
really help administrators, trying  to enforce
MFA in their system.

Therefore, this patch adds the missing endpoint,
which is automatically called for all users, required
to set up MFA, as soon as they have successfully
passed the first authentication step (e.g. username
+ password).

While it's a new endpoint, the actions still call the
MFA providers the same way, the MFA configuration
module does. Therefore, no changes to the API.

Resolves: #95287
Releases: master
Change-Id: Ib82ae53cbd5bd0782418d81d166c1f3d7e9a7ab1
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71132


Tested-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>