reports: increase database timeout; add rate limits.

Increase the database timeout to 10 seconds when generating reports.
Generating reports tends to be slow, especially for things like graphing
posts over time since the beginning of Danbooru.

Does not apply to anonymous users. Users must have an account to get
higher timeouts so that we can identify users scraping reports too hard.

Also add a rate limit of 1 report per 3 seconds to limit abuse.

app/controllers/reports_controller.rb

@@ -3,6 +3,8 @@
 class ReportsController < ApplicationController
   respond_to :html, :json, :xml
 
+  rate_limit :show, rate: 1.0/3.seconds, burst: 15
+
   def index
   end
 
@@ -75,7 +77,16 @@ class ReportsController < ApplicationController
     @from = params.dig(:search, :from) || 1.month.ago
     @to = params.dig(:search, :to) || Time.zone.now
 
-    @results = @model.search(params[:search], CurrentUser.user).timeseries(period: @period, from: @from, to: @to, columns: @columns)
+    if CurrentUser.user.is_member? && CurrentUser.user.statement_timeout < 10_000
+      @statement_timeout = 10_000
+    else
+      @statement_timeout = CurrentUser.user.statement_timeout
+    end
+
+    ApplicationRecord.set_timeout(@statement_timeout) do
+      @results = @model.search(params[:search], CurrentUser.user).timeseries(period: @period, from: @from, to: @to, columns: @columns)
+    end
+
     respond_with(@results)
   end
 end