add template personalisation redaction

If passing in `redact_personalisation` to the template update endpoint,
we should mark that template permanently as redacted - this means that
we won't ever return the personalisation for any notifications for it.

This is to be used with templates containing one time passwords, 2FA
codes or other sensitive information that you may not want service
workers to be able to see.

This is implemented via a separate table, `template_redacted`, which
just contains when the template was redacted.

migrations/versions/0102_template_redacted.py

@@ -0,0 +1,31 @@
+"""empty message
+
+Revision ID: db6d9d9f06bc
+Revises: 0101_een_logo
+Create Date: 2017-06-27 15:37:28.878359
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'db6d9d9f06bc'
+down_revision = '0101_een_logo'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+def upgrade():
+    op.create_table('template_redacted',
+        sa.Column('template_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column('redact_personalisation', sa.Boolean(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_by_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.ForeignKeyConstraint(['template_id'], ['templates.id'], ),
+        sa.ForeignKeyConstraint(['updated_by_id'], ['users.id'], ),
+        sa.PrimaryKeyConstraint('template_id')
+    )
+    op.create_index(op.f('ix_template_redacted_updated_by_id'), 'template_redacted', ['updated_by_id'], unique=False)
+
+
+def downgrade():
+    op.drop_table('template_redacted')