Display SDG icons alongside tags

We're using the translation fallbacks for the icons, just like we do for
texts.

Note we use the `render?` method provided by view_component to make sure
the component will not be rendered when certain features are disabled.

Also note the `find_asset` method works differently in development and
production, and so we use different approaches here.

app/components/sdg/goals/icon_component.html.erb

@@ -0,0 +1 @@
+<%= image_tag image_path, alt: image_text, class: "sdg-goal-icon" %>

app/components/sdg/goals/icon_component.rb

@@ -0,0 +1,32 @@
+class SDG::Goals::IconComponent < ApplicationComponent
+  attr_reader :goal
+  delegate :code, to: :goal
+
+  def initialize(goal)
+    @goal = goal
+  end
+
+  def image_path
+    "sdg/#{folder}/goal_#{code}.png"
+  end
+
+  private
+
+    def image_text
+      goal.code_and_title
+    end
+
+    def folder
+      [*I18n.fallbacks[I18n.locale], "default"].find do |locale|
+        find_asset("sdg/#{locale}/goal_#{code}.png")
+      end
+    end
+
+    def find_asset(path)
+      if Rails.application.assets
+        Rails.application.assets.find_asset(path)
+      else
+        Rails.application.assets_manifest.assets[path]
+      end
+    end
+end

app/components/sdg/goals/tag_list_component.html.erb

@@ -0,0 +1 @@
+<%= link_list(*links, class: "sdg-goal-tag-list") %>

app/components/sdg/goals/tag_list_component.rb

@@ -0,0 +1,57 @@
+class SDG::Goals::TagListComponent < ApplicationComponent
+  attr_reader :record, :limit
+  delegate :link_list, to: :helpers
+
+  def initialize(record, limit: nil)
+    @record = record
+    @limit = limit
+  end
+
+  def render?
+    SDG::ProcessEnabled.new(record.class.name).enabled?
+  end
+
+  private
+
+    def links
+      [*goal_links, see_more_link]
+    end
+
+    def goal_links
+      goals.limit(limit).map do |goal|
+        [
+          render(SDG::Goals::IconComponent.new(goal)),
+          index_by_goal(goal),
+          title: filter_text(goal)
+        ]
+      end
+    end
+
+    def goals
+      record.sdg_goals.order(:code)
+    end
+
+    def see_more_link
+      return unless limit && count_out_of_limit > 0
+
+      [
+        "#{count_out_of_limit}+",
+        polymorphic_path(record),
+        class: "more-goals", title: t("sdg.goals.filter.more", count: count_out_of_limit)
+      ]
+    end
+
+    def index_by_goal(goal)
+      polymorphic_path(record.class, advanced_search: { goal: goal.code })
+    end
+
+    def filter_text(goal)
+      t("sdg.goals.filter.link",
+        resources: record.model_name.human(count: :other),
+        code: goal.code)
+    end
+
+    def count_out_of_limit
+      goals.size - limit
+    end
+end