* add functionality to assemble some config items (like the DB
  connection string) from their parts
* this was previously implemented in our `invenio.cfg`, but more flaky
  because it had to deal with parsing and setting environment variables
* also refactor the startup module

* sometimes the cleanup operations for failed file uploads seem to leave
  over some `FileInstance` entries in the database that have a null URI
* these file instances cause the periodic health checks to fail and
  trigger warning emails

* this enables users to set an alternative email address to which
  notifications will be sent, in case they don't like to use their
  institutional email address

* this can be very useful for having a single project that is used for
  both "local" and "containerized" execution, where some configuration
  items should be slightly different for either (e.g. `SEARCH_HOSTS`)
* currently we have this functionality implemented in our `invenio.cfg`
  but there it is a bit awkward due to the fact that environment
  variables have not been translated into `app.config` yet

* this brings it more in line with the request notifications
* previously we were restricted to emails, now it will be whatever
  notification backends we use
* also remove the mail templates - they now live in code until we
  enhance the notification backend to be more flexible w.r.t. the
  rendered templates

* previously, the global was still set to the original Flask config
  which may not be in sync with the overridden config and thus cause
  unexpected behavior

* fix links being formatted in MD rather than reST
* mention the new submission review workflow, notification backends, and
  background tasks

* this makes sure that our custom translations will be picked up, if we
  ever go for translations

* forward extra arguments to pybabel
* add missing fixed argument to "extract"
* provide better usage information

* they're now built into the compiler:
  https://jinja.palletsprojects.com/en/stable/changes/#version-3-0-0

* because otherwise, `url_for()` will prefer that value over the HTTP
  Host header value
* this causes issues for us with our multi-domain setup, in conjunction
  with the OIDC redirects - given that `SERVER_NAME` can only be a
  scalar value, trying to login on a secondary domain will redirect to
  the primary one and typically fail (because sessions are different, etc.)
* also make sure that the `APP_ALLOWED_HOSTS` config contains the
  `SERVER_NAME` if set

* apparently it was a leftover `before_first_request` handler
* reworked it as `finalize_app` entrypoint
* also, added a check if the app config is already a TUW config to avoid
  unnecessary nesting

* to fix our multi-domain setup with Flask 2.x and 3.0
* see: https://github.com/pallets/flask/pull/5634
* this can be removed once we get Flask 3.1+ in

* create dedicated modules for curations & notifications to separate the
  general notifications infrastructure from the curations-related parts
  (and requests)
* split large modules into smaller logical groups
* split tasks.py into three separate parts: curations, TISS, and general

* automatic accept of submissions for the test system
* reminder for uploaders about accepted but still unpublished records
* reminder for reviewers about open curation requests

* to support our notification use-cases

* to add custom headers that can be used for automatic mail processing
  rules

* also start kicking out infrastructure for the "trusted-publisher" role
  which hasn't been used in a good while now
* instead, if curation isn't enabled, it's up to the admins to publish
  records

* tell it where to find the coverage report

* to make it more obvious that they are all related to user models
* also, rename the modules to better reflect their content
* also, rename some content (e.g. `CurationForm` to `CurationPreferencesForm`)

* they come in handy for the tests, to avoid a dependency on
  Invenio-Theme-TUW