Apply StringConcatenation rule in some places

This rule was added in Rubocop 0.89.0. However, there are some false
positives when we don't use interpolation but simply concatenate in
order to avoid long lines. Even if there weren't false positives, there
are places where we concatenate to emphasize the point that we're adding
a certain character to a text.

We might reconsider this rule in the future, since we generally prefer
interpolation over concatenation.

app/helpers/followables_helper.rb

@@ -14,7 +14,7 @@ module FollowablesHelper
     return unless follow.followable.present?
 
     followable = follow.followable
-    partial = followable_class_name(followable) + "_follow"
+    partial = "#{followable_class_name(followable)}_follow"
     locals = { followable_class_name(followable).to_sym => followable }
 
     render partial, locals

app/helpers/tracks_helper.rb

@@ -3,7 +3,7 @@ module TracksHelper
     track_data = ""
     prefix = " data-track-event-"
     data.each do |key, value|
-      track_data = track_data + prefix + key.to_s + "=" + value + " "
+      track_data = "#{track_data}#{prefix}#{key}=#{value} "
     end
     content_for :track_event do
       track_data

app/helpers/verification_helper.rb

@@ -21,6 +21,6 @@ module VerificationHelper
     data_to_mask    = match[2]
     email_provider  = match[3]
 
-    data_to_display + "*" * data_to_mask.size + "@" + email_provider
+    "#{data_to_display}#{"*" * data_to_mask.size}@#{email_provider}"
   end
 end

app/helpers/votes_helper.rb

@@ -7,9 +7,9 @@ module VotesHelper
     return "0%" if debate.total_votes == 0
 
     if vote == "likes"
-      debate_percentage_of_likes(debate).to_s + "%"
+      "#{debate_percentage_of_likes(debate)}%"
     elsif vote == "dislikes"
-      (100 - debate_percentage_of_likes(debate)).to_s + "%"
+      "#{100 - debate_percentage_of_likes(debate)}%"
     end
   end
 

db/dev_seeds/admin_notifications.rb

@@ -7,7 +7,7 @@ section "Creating Admin Notifications & Templates" do
              "people will discuss & support it.",
     body_es: "Recuerda que puedes crear propuestas y los ciudadanos las debatirán y apoyarán.",
 
-    link: Setting["url"] + "/proposals",
+    link: "#{Setting["url"]}/proposals",
     segment_recipient: "administrators"
   ).deliver
 

spec/system/admin/homepage/homepage_spec.rb

@@ -22,7 +22,7 @@ describe "Homepage" do
     scenario "Admin menu links to homepage path" do
       visit new_admin_widget_card_path(header_card: true)
 
-      click_link Setting["org_name"] + " Administration"
+      click_link "#{Setting["org_name"]} Administration"
 
       expect(page).to have_current_path(admin_root_path)
     end

spec/system/admin/site_customization/documents_spec.rb

@@ -58,7 +58,7 @@ describe "Documents" do
   scenario "Create" do
     visit new_admin_site_customization_document_path
 
-    attach_file("document_attachment", Rails.root + "spec/fixtures/files/logo.pdf")
+    attach_file("document_attachment", "#{Rails.root}/spec/fixtures/files/logo.pdf")
     click_button "Upload"
 
     expect(page).to have_content "Document uploaded succesfully"

spec/system/social_media_meta_tags_spec.rb

@@ -33,8 +33,7 @@ describe "Social media meta tags" do
 
       expect(page).to have_property "og:title", with: meta_title
       expect(page).to have_property "article:publisher", with: url
-      expect(page).to have_property "article:author", with: "https://www.facebook.com/" +
+      expect(page).to have_property "article:author", with: "https://www.facebook.com/#{facebook_handle}"
-                                                             facebook_handle
       expect(page).to have_property "og:url", with: "#{Capybara.app_host}/"
       expect(page).to have_property "og:image", with: "#{Capybara.app_host}/social_media_icon.png"
       expect(page).to have_property "og:site_name", with: org_name