add entry requests, invite new users

app/mailers/invitation_mailer.rb

@@ -1,12 +1,19 @@
 class InvitationMailer < ApplicationMailer
-  def invite(user)
+  def invite(user, approved_entry: nil)
     @user = user
+    @approved_entry = approved_entry
     @invitation_url = invitation_url(@user.invitation_token)
     @expires_at = @user.invitation_sent_at + User::INVITATION_TOKEN_EXPIRY
 
+    subject = if @approved_entry
+      "Your entry request has been approved - Join Sanasto Wiki"
+    else
+      "You've been invited to join Sanasto Wiki"
+    end
+
     mail(
       to: @user.email,
-      subject: "You've been invited to join Sanasto Wiki"
+      subject: subject
     )
   end
 end