Rename filter method to filter_by

Ruby 2.6 introduces `Enumerable#filter` as an alias to
`Enumerable#select`, and so our Filterable.filter method will not work
with Ruby 2.6.

So we're renaming the method to `filter_by`, which is similar to
`find_by`. We could also change the `filter` method so if a block is
given it delegates to `Enumerable#filter`, the same way ActiveRecord
handles the `select` method, but IMHO this is easier to follow.

app/controllers/concerns/commentable_actions.rb

@@ -9,7 +9,7 @@ module CommentableActions
 
     @resources = @current_order == "recommendations" && current_user.present? ? @resources.recommendations(current_user) : @resources.for_render
     @resources = @resources.search(@search_terms) if @search_terms.present?
-    @resources = @advanced_search_terms.present? ? @resources.filter(@advanced_search_terms) : @resources
+    @resources = @advanced_search_terms.present? ? @resources.filter_by(@advanced_search_terms) : @resources
 
     @resources = @resources.page(params[:page]).send("sort_by_#{@current_order}")
 

app/models/budget/investment.rb

@@ -357,7 +357,7 @@ class Budget
       investments = investments.send(current_filter)             if current_filter.present?
       investments = investments.by_heading(params[:heading_id])  if params[:heading_id].present?
       investments = investments.search(params[:search])          if params[:search].present?
-      investments = investments.filter(params[:advanced_search]) if params[:advanced_search].present?
+      investments = investments.filter_by(params[:advanced_search]) if params[:advanced_search].present?
       investments
     end
 

app/models/concerns/filterable.rb

@@ -7,7 +7,7 @@ module Filterable
   end
 
   class_methods do
-    def filter(params)
+    def filter_by(params)
       resources = all
       params.each do |filter, value|
         if allowed_filter?(filter, value)