Rework the persistence layer

1. Simplify the exposed api to reduce race conditions
   which could occur if we allowed flow details, task
   details and log books to be deleted at different
   times; reduce this down to just being able to save and
   delete from logbooks (and only save/update for flow
   and task details to) to reduce the problem cases.
2. Introduce a alembic migration with a proper schema so that
   the initial database can be created in the first place,
   adjust its exposed fields and relations to be defined
   by said schema.
3. Use oslo db models instead of our own.

Change-Id: I78bbedf87d506d3f39157198638937c933235b7b

1 files changed, 22 insertions, 0 deletions

diff --git a/taskflow/persistence/backends/sqlalchemy/alembic/script.py.mako b/taskflow/persistence/backends/sqlalchemy/alembic/script.py.mako
new file mode 100644
index 0000000..9570201
--- /dev/null
+++ b/taskflow/persistence/backends/sqlalchemy/alembic/script.py.mako
@@ -0,0 +1,22 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision}
+Create Date: ${create_date}
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}