add /costs permalink (closes #4819)

app/controllers/Main.scala

@@ -161,6 +161,10 @@ Disallow: /games/export
     Ok(html.site.getFishnet()).fuccess
   }
 
+  def costs = Open { implicit ctx =>
+    Redirect("https://docs.google.com/spreadsheets/d/1CGgu-7aNxlZkjLl9l-OlL00fch06xp0Q7eCVDDakYEE/preview").fuccess
+  }
+
   def contact = Open { implicit ctx =>
     Ok(html.site.contact()).fuccess
   }

app/views/plan/index.scala.html

@@ -197,7 +197,7 @@ csp = defaultCsp.withStripe.some) {
         <dd>
           First of all, powerful servers.<br />
           Then we pay a full-time developer: @userIdLink("thibault".some), the founder of Lichess.<br />
-          See the <a href="https://docs.google.com/spreadsheets/d/1CGgu-7aNxlZkjLl9l-OlL00fch06xp0Q7eCVDDakYEE/preview" target="_blank">detailed cost breakdown</a>.
+          See the <a href="/costs" target="_blank">detailed cost breakdown</a>.
         </dd>
         <dt>Is Lichess an official non-profit?</dt>
         <dd>

conf/base.conf

@@ -626,7 +626,7 @@ plan {
     patron = plan_patron
     charge = plan_charge
   }
-  monthly_goal = 8072 # https://docs.google.com/spreadsheets/d/1CGgu-7aNxlZkjLl9l-OlL00fch06xp0Q7eCVDDakYEE/preview
+  monthly_goal = 8072 # https://lichess.org/costs
 }
 hub {
   actor {

conf/routes

@@ -584,6 +584,7 @@ GET   /mobile                          controllers.Main.mobile
 GET   /lag                             controllers.Main.lag
 GET   /fpmenu                          controllers.Main.fpmenu
 GET   /get-fishnet                     controllers.Main.getFishnet
+GET   /costs                           controllers.Main.costs
 
 # Dev
 GET   /dev/cli                         controllers.Dev.cli