Added user login & registration. Added SQL file for postgres database.

backend/nestjs-seshat-api/src/auth/guards/login-auth.guard.ts

@@ -0,0 +1,6 @@
+
+import { Injectable } from '@nestjs/common';
+import { AuthGuard } from '@nestjs/passport';
+
+@Injectable()
+export class LoginAuthGuard extends AuthGuard('login') { }