Add new SMS rate for April 1 2021.

Downgrade script isn't necessary.

migrations/versions/0350_update_rates.py

@@ -0,0 +1,23 @@
+"""
+
+Revision ID: 0350_update_rates
+Revises: 0349_add_ft_processing_time
+Create Date: 2021-04-01 08:00:24.775338
+
+"""
+import uuid
+
+from alembic import op
+
+revision = '0350_update_rates'
+down_revision = '0349_add_ft_processing_time'
+
+
+def upgrade():
+    op.get_bind()
+    op.execute("INSERT INTO rates(id, valid_from, rate, notification_type) "
+               "VALUES('{}', '2021-03-31 23:00:00', 0.0160, 'sms')".format(uuid.uuid4()))
+
+
+def downgrade():
+    pass