Use cache for user info data.

Later these should be persisted in the user.

lib/pleroma/user.ex

@@ -122,4 +122,9 @@ def get_cached_by_nickname(nickname) do
     key = "nickname:#{nickname}"
     Cachex.get!(:user_cache, key, fallback: fn(_) -> Repo.get_by(User, nickname: nickname) end)
   end
+
+  def get_cached_user_info(user) do
+    key = "user_info:#{user.id}"
+    Cachex.get!(:user_cache, key, fallback: fn(_) -> user_info(user) end)
+  end
 end

lib/pleroma/web/twitter_api/representers/user_representer.ex

@@ -11,7 +11,7 @@ def to_map(user, opts) do
       false
     end
 
-    user_info = User.user_info(user)
+    user_info = User.get_cached_user_info(user)
 
     map = %{
       "id" => user.id,