Create sqlalchemy_searchable expressions (#6491)

The required sql expressions for sqlalchemy_searchable are only created
on the sqlalchemy pre_create hook. When upgrading from a previous redash
version no CREATE statements may be run, so these expressions are never
created.

Add a migration to manually execute the sql_expressions DDL from
sqlalchemy_searchable.

migrations/versions/7ce5925f832b_create_sqlalchemy_searchable_expressions.py

@@ -0,0 +1,25 @@
+"""create sqlalchemy_searchable expressions
+
+Revision ID: 7ce5925f832b
+Revises: 1038c2174f5d
+Create Date: 2023-09-29 16:48:29.517762
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy_searchable import sql_expressions
+
+
+# revision identifiers, used by Alembic.
+revision = '7ce5925f832b'
+down_revision = '1038c2174f5d'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.execute(sql_expressions)
+
+
+def downgrade():
+    pass