Apply location filters from API

This makes it consistent with the sources etc which filter out 'Direct /
None' on the API side. These filters are used by both the native and
imported data handling code, which would otherwise both duplicate the
filters in their `where` clauses.

lib/plausible/stats/breakdown.ex

@@ -393,7 +393,6 @@ defmodule Plausible.Stats.Breakdown do
     from(
       s in q,
       group_by: s.country_code,
-      where: s.country_code != "\0\0",
       select_merge: %{country: s.country_code}
     )
   end
@@ -402,7 +401,6 @@ defmodule Plausible.Stats.Breakdown do
     from(
       s in q,
       group_by: s.subdivision1_code,
-      where: s.subdivision1_code != "",
       select_merge: %{region: s.subdivision1_code}
     )
   end
@@ -411,7 +409,6 @@ defmodule Plausible.Stats.Breakdown do
     from(
       s in q,
       group_by: s.city_geoname_id,
-      where: s.city_geoname_id != 0,
       select_merge: %{city: s.city_geoname_id}
     )
   end

lib/plausible/stats/imported.ex

@@ -154,14 +154,10 @@ defmodule Plausible.Stats.Imported do
           imported_q |> select_merge([i], %{country: i.country})
 
         :region ->
-          imported_q
-          |> select_merge([i], %{region: i.region})
-          |> where([i], i.region != "")
+          imported_q |> select_merge([i], %{region: i.region})
 
         :city ->
-          imported_q
-          |> select_merge([i], %{city: i.city})
-          |> where([i], i.city != 0)
+          imported_q |> select_merge([i], %{city: i.city})
 
         :device ->
           imported_q |> select_merge([i], %{device: i.device})

lib/plausible_web/controllers/api/stats_controller.ex

@@ -564,7 +564,12 @@ defmodule PlausibleWeb.Api.StatsController do
 
   def countries(conn, params) do
     site = conn.assigns[:site]
-    query = Query.from(site.timezone, params) |> Filters.add_prefix()
+
+    query =
+      Query.from(site.timezone, params)
+      |> Filters.add_prefix()
+      |> Query.put_filter("visit:country", {:is_not, "\0\0"})
+
     pagination = parse_pagination(params)
 
     countries =
@@ -614,7 +619,12 @@ defmodule PlausibleWeb.Api.StatsController do
 
   def regions(conn, params) do
     site = conn.assigns[:site]
-    query = Query.from(site.timezone, params) |> Filters.add_prefix()
+
+    query =
+      Query.from(site.timezone, params)
+      |> Filters.add_prefix()
+      |> Query.put_filter("visit:region", {:is_not, ""})
+
     pagination = parse_pagination(params)
 
     regions =
@@ -646,7 +656,12 @@ defmodule PlausibleWeb.Api.StatsController do
 
   def cities(conn, params) do
     site = conn.assigns[:site]
-    query = Query.from(site.timezone, params) |> Filters.add_prefix()
+
+    query =
+      Query.from(site.timezone, params)
+      |> Filters.add_prefix()
+      |> Query.put_filter("visit:city", {:is_not, 0})
+
     pagination = parse_pagination(params)
 
     cities =