[Bookworm] Correct Flask DB migration process

Move the old manage script to _legacy, and add a new _flask version with
modern Flask tooling. Decide which one to call via pvc-api-db-migrate
using /etc/debian_version call.

api-daemon/pvc-api-db-upgrade

@@ -11,5 +11,16 @@ if [[ ! -f ${PVC_CONFIG_FILE} ]]; then
 fi
 
 pushd /usr/share/pvc
-./pvcapid-manage.py db upgrade
+
+case "$( cat /etc/debian_version )" in
+    10.*|11.*)
+        # Debian 10 & 11
+        ./pvcapid-manage_legacy.py db upgrade
+    ;;
+    *)
+        # Debian 12+
+        flask --app ./pvcapid-manage_flask.py db upgrade
+    ;;
+esac
+
 popd

api-daemon/pvcapid-manage_flask.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+
+# pvcapid-manage_flask.py - PVC Database management tasks (via Flask CLI)
+# Part of the Parallel Virtual Cluster (PVC) system
+#
+#    Copyright (C) 2018-2022 Joshua M. Boniface <joshua@boniface.me>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, version 3.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+###############################################################################
+
+from pvcapid.flaskapi import app, db
+from pvcapid.models import *  # noqa F401,F403
+
+from flask_migrate import Migrate
+
+migrate = Migrate(app, db)
+
+# Call flask --app /usr/share/pvc/pvcapid-manage_flask.py db upgrade

api-daemon/pvcapid-manage_legacy.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 
-# manage.py - PVC Database management tasks
+# pvcapid-manage_legacy.py - PVC Database management tasks (Legacy)
 # Part of the Parallel Virtual Cluster (PVC) system
 #
 #    Copyright (C) 2018-2022 Joshua M. Boniface <joshua@boniface.me>