Fix flavor reservation before_end code

This is a customization in our fork, and so needed fixing.
Email relay is configured under the host plugin still based on our email script. See
ChameleonCloud/kolla-containers@ee83055:

blazar/db/migration/alembic_migrations/versions/a167bcf47857_add_flavor_before_end.py

@@ -0,0 +1,41 @@
+# Copyright 2025 OpenStack Foundation.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Add flavor before end column
+
+Revision ID: a167bcf47857
+Revises: 95bd85fe13f0
+Create Date: 2025-01-27 19:02:30.182818
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'a167bcf47857'
+down_revision = '95bd85fe13f0'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('instance_reservations', sa.Column('before_end', sa.String(length=36), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('instance_reservations', 'before_end')
+    # ### end Alembic commands ###

blazar/db/sqlalchemy/models.py

@@ -245,6 +245,7 @@ class InstanceReservations(mb.BlazarBase, mb.SoftDeleteMixinWithUuid):
     flavor_id = sa.Column(sa.String(36), nullable=True)
     aggregate_id = sa.Column(sa.Integer, nullable=True)
     server_group_id = sa.Column(sa.String(36), nullable=True)
+    before_end = sa.Column(sa.String(36))
 
 
 class ComputeHostAllocation(mb.BlazarBase, mb.SoftDeleteMixinWithUuid):

blazar/plugins/flavor/flavor_plugin.py

@@ -42,6 +42,9 @@
 
 LOG = logging.getLogger(__name__)
 
+
+before_end_options = ['', 'snapshot', 'default', 'email']
+
 QUERY_TYPE_ALLOCATION = 'allocation'
 
 
@@ -74,6 +77,11 @@ def query_allocations(self, hosts, lease_id=None, reservation_id=None):
 
     def allocation_candidates(self, reservation):
         """Return a list of candidate host_ids."""
+        if 'before_end' not in reservation:
+            reservation['before_end'] = 'default'
+        if reservation['before_end'] not in before_end_options:
+            raise mgr_exceptions.MalformedParameter(param='before_end')
+
         host_ids, _ = self._pick_hosts(reservation)
         return host_ids