feat(backend): add sqlite migrations + app state + tests

backend/include/csp/app_state.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "csp/db/sqlite_db.h"
+
+#include <memory>
+#include <string>
+
+namespace csp {
+
+class AppState {
+ public:
+  static AppState& Instance();
+
+  void Init(const std::string& sqlite_path);
+
+  db::SqliteDb& db();
+
+ private:
+  AppState() = default;
+
+  std::unique_ptr<db::SqliteDb> db_;
+};
+
+}  // namespace csp

backend/include/csp/db/sqlite_db.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <sqlite3.h>
+
+#include <memory>
+#include <string>
+
+namespace csp::db {
+
+class SqliteDb {
+ public:
+  static SqliteDb OpenFile(const std::string& path);
+  static SqliteDb OpenMemory();
+
+  SqliteDb() = default;
+  ~SqliteDb();
+
+  SqliteDb(const SqliteDb&) = delete;
+  SqliteDb& operator=(const SqliteDb&) = delete;
+
+  SqliteDb(SqliteDb&& other) noexcept;
+  SqliteDb& operator=(SqliteDb&& other) noexcept;
+
+  sqlite3* raw() const { return db_; }
+
+  void Exec(const std::string& sql);
+
+ private:
+  explicit SqliteDb(sqlite3* db) : db_(db) {}
+
+  sqlite3* db_ = nullptr;
+};
+
+// Apply SQL migrations in order. For now we ship a single init migration.
+void ApplyMigrations(SqliteDb& db);
+
+}  // namespace csp::db