batch add students: add optional group selection in batch modal

db/migration.sql

@@ -0,0 +1,32 @@
+CREATE TABLE IF NOT EXISTS students (
+  id SERIAL PRIMARY KEY,
+  name VARCHAR(150) NOT NULL UNIQUE,
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
+ALTER TABLE students ADD COLUMN IF NOT EXISTS group_id INT REFERENCES groups(id);
+
+CREATE TABLE IF NOT EXISTS settings (
+  key TEXT PRIMARY KEY,
+  value TEXT
+);
+
+INSERT INTO settings (key, value) VALUES ('spam_interval_min', '30')
+ON CONFLICT (key) DO NOTHING;
+
+CREATE TABLE IF NOT EXISTS share_links (
+  id SERIAL PRIMARY KEY,
+  token VARCHAR(40) UNIQUE NOT NULL,
+  name VARCHAR(200) NOT NULL,
+  group_id INT REFERENCES groups(id),
+  date_from DATE,
+  date_to DATE,
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
+DO $$
+BEGIN
+  INSERT INTO students (name)
+  SELECT DISTINCT student_name FROM entries WHERE student_name IS NOT NULL AND student_name <> ''
+  ON CONFLICT (name) DO NOTHING;
+END $$;