Added table and model for letter rates.

The rates for the letters are per page, therefore it seemed better to build a different table.

app/models.py

@@ -1141,3 +1141,20 @@ class JobStatistics(db.Model):
         )
         the_string += "created at {}".format(self.created_at)
         return the_string
+
+
+class LetterRate(db.Model):
+    __tablename__ = 'letter_rates'
+
+    id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    valid_from = valid_from = db.Column(db.DateTime, nullable=False)
+
+
+class LetterRateDetail(db.Model):
+    __tablename__ = 'letter_rate_details'
+
+    id = db.Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    letter_rate_id = db.Column(UUID(as_uuid=True), db.ForeignKey('letter_rates.id'), index=True, nullable=False)
+    letter_rate = db.relationship('LetterRate', backref='letter_rates')
+    page_total = db.Column(db.Integer, nullable=False)
+    rate = db.Column(db.Numeric(), nullable=False)

migrations/versions/0088_letter_billing.py

@@ -0,0 +1,50 @@
+"""empty message
+
+Revision ID: 0088_letter_billing
+Revises: 0087_scheduled_notifications
+Create Date: 2017-05-31 11:43:55.744631
+
+"""
+import uuid
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+revision = '0088_letter_billing'
+down_revision = '0087_scheduled_notifications'
+
+
+def upgrade():
+    op.create_table('letter_rates',
+                    sa.Column('id', postgresql.UUID(as_uuid=True), nullable=False),
+                    sa.Column('valid_from', sa.DateTime(), nullable=False),
+                    sa.PrimaryKeyConstraint('id')
+                    )
+    op.create_table('letter_rate_details',
+                    sa.Column('id', postgresql.UUID(as_uuid=True), nullable=False),
+                    sa.Column('letter_rate_id', postgresql.UUID(as_uuid=True), nullable=False),
+                    sa.Column('page_total', sa.Integer(), nullable=False),
+                    sa.Column('rate', sa.Numeric(), nullable=False),
+                    sa.ForeignKeyConstraint(['letter_rate_id'], ['letter_rates.id'], ),
+                    sa.PrimaryKeyConstraint('id')
+                    )
+    op.create_index(op.f('ix_letter_rate_details_letter_rate_id'), 'letter_rate_details', ['letter_rate_id'],
+                    unique=False)
+
+    op.get_bind()
+    letter_id = uuid.uuid4()
+    op.execute("insert into letter_rates(id, valid_from) values('{}', '2017-03-31 23:00:00')".format(letter_id))
+    insert_details = "insert into letter_rate_details(id, letter_rate_id, page_total, rate) values('{}', '{}', {}, {})"
+    op.execute(
+        insert_details.format(uuid.uuid4(), letter_id, 1, 29.3))
+    op.execute(
+        insert_details.format(uuid.uuid4(), letter_id, 2, 32))
+    op.execute(
+        insert_details.format(uuid.uuid4(), letter_id, 3, 35))
+
+
+def downgrade():
+    op.get_bind()
+    op.drop_index('ix_letter_rate_details_letter_rate_id')
+    op.drop_table('letter_rate_details')
+    op.drop_table('letter_rates')