def block(user)
      friendship = find_any_friendship_with(user)
      return false if friendship.nil? || !friendship.can_block?(self)
      friendship.update_attribute(:blocker, self)
    end
def block(user)
      friendship = find_any_friendship_with(user)
      return false if friendship.nil? || !friendship.can_block?(self)
      friendship.update_attribute(:blocker, self)
    end
blocks a friendship