Add CommunitySolution

* Also slightly refactor some JS files

app/models/community_solution_lock.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class CommunitySolutionLock < ApplicationRecord
+  include Creation
+
+  belongs_to :community_solution
+  has_many :community_solution_contributions
+
+  validates :locked_until, presence: true
+
+  def active?
+    Time.zone.now <= locked_until
+  end
+
+  def working_time
+    ActiveSupport::Duration.build(locked_until - created_at)
+  end
+end