Add storage location field to battery with dynamic dropdown

Dropdown populated from existing distinct storage locations,
with 'New location...' option revealing a text input.

app.py

@@ -86,7 +86,13 @@ def create_app(config_object="config"):
         battery = db.get(Battery, battery_id)
         if battery is None:
             abort(404)
-        return render_template("battery_detail.html", battery=battery)
+        storage_locations = [
+            r[0] for r in db.query(Battery.storage_location)
+            .filter(Battery.storage_location.isnot(None))
+            .distinct().order_by(Battery.storage_location).all()
+        ]
+        return render_template("battery_detail.html", battery=battery,
+                               storage_locations=storage_locations)
 
     # ------------------------------------------------------------------ #
     # Battery — edit notes
@@ -114,6 +120,7 @@ def create_app(config_object="config"):
         battery.tested_date         = f.get("tested_date", "").strip() or None
         battery.charge_cycles       = _int("charge_cycles")
         battery.purchase_date       = f.get("purchase_date", "").strip() or None
+        battery.storage_location    = f.get("storage_location", "").strip() or None
 
         db.commit()
         flash("Details updated.", "success")