Add Client.archived flag, ignore archived for "disabled probes" check

this lets us keep old client config around without deleting it, but it should
not interfere with other logic etc.

rattail_tempmon/db/alembic/versions/e9eb7fc0a451_add_client_archived.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8; -*-
+"""add client.archived
+
+Revision ID: e9eb7fc0a451
+Revises: 75c09e11543c
+Create Date: 2018-09-28 12:12:19.813042
+
+"""
+
+from __future__ import unicode_literals, absolute_import
+
+# revision identifiers, used by Alembic.
+revision = 'e9eb7fc0a451'
+down_revision = u'75c09e11543c'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+import sqlalchemy as sa
+import rattail.db.types
+
+
+
+def upgrade():
+
+    # client
+    op.add_column('client', sa.Column('archived', sa.Boolean(), nullable=True))
+    client = sa.sql.table('client', sa.sql.column('archived'))
+    op.execute(client.update().values({'archived': False}))
+    op.alter_column('client', 'archived', nullable=False)
+
+
+def downgrade():
+
+    # client
+    op.drop_column('client', 'archived')

rattail_tempmon/db/model.py

@@ -63,6 +63,14 @@ class Client(Base):
     enabled = sa.Column(sa.Boolean(), nullable=False, default=False)
     online = sa.Column(sa.Boolean(), nullable=False, default=False)
 
+    archived = sa.Column(sa.Boolean(), nullable=False, default=False, doc="""
+    Flag indicating this client is "archived".  This typically means that the
+    client itself no longer exists etc. but that the configuration for it
+    should be retained, e.g. to be used as a reference later etc.  Note that
+    "archiving" a client is different from "disabling" it; the latter being
+    more temporary.
+    """)
+
     def __str__(self):
         return '{} ({})'.format(self.config_key, self.hostname)