Added socket logic for notifications

src/notifications/notification.entity.ts

+import { Entity, PrimaryGeneratedColumn, Column, CreateDateColumn } from "typeorm";
+
+// temporary table for warning notifications
+@Entity('Notifications')
+export class NotificationEntity {
+    @PrimaryGeneratedColumn('uuid') id: string;
+    @Column({type: 'text'}) message: string;
+    @CreateDateColumn() issued: Date;
+    // TODO:
+    // when game creation has been implemented, add logic so that the notifications are tied to games
+}
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