Add first day of the week feature to user settings and calendar functionality

backend/sql/version_1.sql

@@ -17,6 +17,8 @@ CREATE TABLE [User] (
 
     [default_servings] INTEGER DEFAULT 4,
     [lang] TEXT NOT NULL DEFAULT 'en',
+    -- 0: Monday, 1: Tuesday, 2: Wednesday, 3: Thursday, 4: Friday, 5: Saturday, 6: Sunday.
+    [first_day_of_the_week] INTEGER DEFAULT 0,
 
     [password] TEXT NOT NULL, -- argon2(password_plain, salt).
 
@@ -34,6 +36,17 @@ CREATE TABLE [User] (
 CREATE INDEX [validation_token_index] ON [User]([validation_token]);
 CREATE UNIQUE INDEX [User_email_index] ON [User]([email]);
 
+CREATE TRIGGER [User_trigger_update_first_day_of_the_week]
+BEFORE UPDATE OF [first_day_of_the_week]
+ON [User]
+BEGIN
+    SELECT
+        CASE
+            WHEN NEW.[first_day_of_the_week] < 0 OR NEW.[first_day_of_the_week] > 6 THEN
+                RAISE (ABORT, 'Invalid [first_day_of_the_week] value')
+        END;
+END;
+
 CREATE TABLE [UserLoginToken] (
     [id] INTEGER PRIMARY KEY,
     [user_id] INTEGER NOT NULL,