Enable deep linking to a category group and category

[struan]

Now that we allow a category to exist in multiple groups it's not possible to create a deep link that will pre select a category in only one of the groups it is in.

e.g if you have the following:

• Roads
  • Potholes
  • Flooding
• Pavements
  • Potholes
  • Damaged paving

And wish to select only Roads -> Potholes it is currently not possible.

Setting filter_category to Potholes will select it in both the Road and Pavements groups. Adding a filter_group=Roads will select all the categories in the Roads group as well.

I suggest that filter_group=Roads&filter_category=Potholes would only select Roads -> Potholes.