Refactor to async TimescaleDB backend & add Alembic migrations

alembic/script.py.mako

@@ -0,0 +1,21 @@
+"""
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = '${up_revision}'
+down_revision = ${repr(down_revision) if down_revision else None}
+branch_labels = ${repr(branch_labels) if branch_labels else None}
+depends_on = ${repr(depends_on) if depends_on else None}
+
+def upgrade():
+    """Upgrade migrations go here."""
+    pass
+
+def downgrade():
+    """Downgrade migrations go here."""
+    pass