docs: def upgrade():
      """Upgrade database."""
      def json_column(name, **kwargs):
          """Return JSON column."""
          return sa.Column(
              name,
              sqlalchemy_utils.types.JSONType().with_variant(
                  postgresql.JSON(none_as_null=True), 'postgresql',
              ),
              **kwargs
          )
  
      op.create_table(
          'webhooks_events',
          sa.Column('created', sa.DateTime(), nullable=False),
          sa.Column('updated', sa.DateTime(), nullable=False),
          sa.Column(
              'id', sqlalchemy_utils.types.uuid.UUIDType(), nullable=False),
          sa.Column('receiver_id', sa.String(length=255), nullable=False),
          sa.Column('user_id', sa.Integer(), nullable=True),
          json_column('payload', nullable=True),
          json_column('payload_headers', nullable=True),
          json_column('response', nullable=True),
          json_column('response_headers', nullable=True),
          sa.Column('response_code', sa.Integer(), nullable=True),
          sa.ForeignKeyConstraint(['user_id'], [u'accounts_user.id'], ),
          sa.PrimaryKeyConstraint('id')
      )
      op.create_index(
          op.f('ix_webhooks_events_receiver_id'),
          'webhooks_events',
          ['receiver_id'],
          unique=False
      )