database: Add fetch() for SessionDao

database/sessiondao.h

@@ -10,6 +10,7 @@ class SessionDao
 	virtual void save(const Session &session) = 0;
 	virtual std::optional<Session> find(std::string token) = 0;
 	virtual void deleteSession(std::string token) = 0;
+	virtual std::vector<Session> fetch() = 0;
 	virtual ~SessionDao()
 	{
 	}