added web and fix some problems

src/db_get_user_by_id.c

@@ -0,0 +1,44 @@
+#include "user.h"
+#include "database.h"
+#include "sql.h"
+
+User *db_get_user_by_id(const int id) {
+    User *user = nullptr;
+  pthread_mutex_lock(&db_mutex);
+  if (!db) {
+    fprintf(stderr, "Database not initialized\n");
+    pthread_mutex_unlock(&db_mutex);
+    return nullptr;
+  }
+  sqlite3_stmt *stmt;
+  int rc =
+      sqlite3_prepare_v2(db, SELECT_USER_BY_ID_SQL, -1, &stmt, nullptr);
+  if (rc != SQLITE_OK) {
+    fprintf(stderr, "Cannot prepare statement: %s\n", sqlite3_errmsg(db));
+    sqlite3_close(db);
+    exit(1);
+  }
+
+  sqlite3_bind_int(stmt, 1, id);
+
+  while ((rc = sqlite3_step(stmt)) == SQLITE_ROW) {
+    int id = sqlite3_column_int(stmt, 0);
+    const unsigned char *db_username = sqlite3_column_text(stmt, 1);
+    const unsigned char *db_email = sqlite3_column_text(stmt, 2);
+    const unsigned char *db_password = sqlite3_column_text(stmt, 3);
+    const unsigned char *db_group = sqlite3_column_text(stmt, 4);
+    int db_is_superuser = sqlite3_column_int(stmt, 5);
+    user = new_user(id, (char *) db_username, (char *) db_password,
+                    (char *) db_email, (char *) db_group, db_is_superuser);
+  }
+
+  if (rc != SQLITE_DONE) {
+    fprintf(stderr, "Error reading data: %s\n", sqlite3_errmsg(db));
+    free_user(user);
+    sqlite3_finalize(stmt);
+    return nullptr;
+  }
+
+  pthread_mutex_unlock(&db_mutex);
+  return user;
+}