feat: add option to change username

fix: rename subscriptions materialized view of the user too

remove materialized views from username change

fix: downcase username and limit username lenght (from routes/login.cr)

Users that changed their username to something like `User`, were unable
to login because the username is downcased on routes/login.cr

src/invidious/routes/account.cr

@@ -78,6 +78,75 @@ module Invidious::Routes::Account
     env.redirect referer
   end
 
+  # -------------------
+  #  Username update
+  # -------------------
+
+  # Show the username change interface (GET request)
+  def get_change_username(env)
+    locale = env.get("preferences").as(Preferences).locale
+
+    user = env.get? "user"
+    sid = env.get? "sid"
+    referer = get_referer(env)
+
+    if !user
+      return env.redirect referer
+    end
+
+    user = user.as(User)
+    sid = sid.as(String)
+    csrf_token = generate_response(sid, {":change_username"}, HMAC_KEY)
+
+    templated "user/change_username"
+  end
+
+  # Handle the username change (POST request)
+  def post_change_username(env)
+    locale = env.get("preferences").as(Preferences).locale
+
+    user = env.get? "user"
+    sid = env.get? "sid"
+    referer = get_referer(env)
+
+    if !user
+      return env.redirect referer
+    end
+
+    user = user.as(User)
+    sid = sid.as(String)
+    token = env.params.body["csrf_token"]?
+
+    begin
+      validate_request(token, sid, env.request, HMAC_KEY, locale)
+    rescue ex
+      return error_template(400, ex)
+    end
+
+    new_username = env.params.body["new_username"]?.try &.downcase.byte_slice(0, 254)
+    if new_username.nil?
+      return error_template(401, "username_required_field")
+    end
+
+    if new_username.empty?
+      return error_template(401, "username_empty")
+    end
+
+    if new_username == user.email
+      return error_template(401, "username_is_the_same")
+    end
+
+    if Invidious::Database::Users.select(email: new_username)
+      return error_template(401, "username_taken")
+    end
+
+    Invidious::Database::Users.update_username(user, new_username.to_s)
+    Invidious::Database::Users.update_user_session_id(user, new_username.to_s)
+    Invidious::Database::Users.update_user_playlists_author(user, new_username.to_s)
+
+    env.redirect referer
+  end
+
   # -------------------
   #  Account deletion
   # -------------------