add user similarity report

app/logical/reports/user_similarity.rb

@@ -0,0 +1,33 @@
+module Reports
+  class UserSimilarity
+    attr_reader :user_id
+
+    def initialize(user_id)
+      @user_id = user_id
+    end
+
+    def user
+      User.find(user_id)
+    end
+
+    def fetch_similar_user_ids
+      return NotImplementedError unless Danbooru.config.report_server
+
+      params = {
+        "key" => Danbooru.config.shared_remote_key,
+        "user_id" => user_id
+      }
+      uri = URI.parse("#{Danbooru.config.listbooru_server}/reports/user_similarity")
+      uri.query = URI.encode_www_form(params)
+
+      Net::HTTP.start(uri.host, uri.port) do |http|
+        resp = http.request_get(uri.request_uri)
+        if resp.is_a?(Net::HTTPSuccess)
+          resp.body
+        else
+          raise "HTTP error code: #{resp.code} #{resp.message}"
+        end
+      end
+    end
+  end
+end