Add Client.disk_type to track SD card vs. USB

i.e. assuming raspberry pi device for the client.  kind of a specific use case
behind this but it seemed like it could be useful generally

rattail_tempmon/db/alembic/versions/5f2b87474433_add_client_disk_type.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8; -*-
+"""add client.disk_type
+
+Revision ID: 5f2b87474433
+Revises: 34041e1032a2
+Create Date: 2018-09-28 19:08:02.743343
+
+"""
+
+from __future__ import unicode_literals, absolute_import
+
+# revision identifiers, used by Alembic.
+revision = '5f2b87474433'
+down_revision = u'34041e1032a2'
+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('disk_type', sa.Integer(), nullable=True))
+
+
+def downgrade():
+
+    # client
+    op.drop_column('client', 'disk_type')

rattail_tempmon/db/model.py

@@ -55,6 +55,12 @@ class Client(Base):
     hostname = sa.Column(sa.String(length=255), nullable=False)
     location = sa.Column(sa.String(length=255), nullable=True)
 
+    disk_type = sa.Column(sa.Integer(), nullable=True, doc="""
+    Integer code representing the type of hard disk used, if known.  The
+    original motivation for this was to keep track of whether each client
+    (aka. Raspberry Pi) was using a SD card or USB drive for the root disk.
+    """)
+
     delay = sa.Column(sa.Integer(), nullable=True, doc="""
     Number of seconds to delay between reading / recording temperatures.  If
     not set, a default of 60 seconds will be assumed.