Create a route to save notification in backend

[dvishal485]

Frontend will send notification in body with type ClientNotification, wrap it in INotification type (by adding extra time field populated with current time), save it in the database. (schema already exists in backend code)

https://github.com/dtutimes/nix-backend-v2/blob/main/src/api/models/notificationModel.ts#L34-L44

https://github.com/dtutimes/nix-backend-v2/blob/main/src/api/models/notificationModel.ts#L54-L62

export interface ClientNotification {
  title: string;
  description: string;
  actions: ClientNotificationAction[];
  link?: string;
}

export interface ClientNotificationAction {
  action: string;
  link: string;
}