Set Cache-Control to no-cache (#1356)

- Adds a Nest interceptor which, when applied, sets the `Cache-Control` directive to `no-cache`. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#directives
- Adjusts the redirects on the `RelayLegacyController`:
  * With `res.redirect`, a response was being sent to the clients, and the interceptor would fail to set the header (resulting in a 500 – "Cannot set headers after they are sent to the client").
  * By returning an object with `{ url }` with the intended redirect in addition to the decorator `@Redirect`, the header is set correctly before the body is sent out to the clients. See https://docs.nestjs.com/controllers#redirection

src/app.module.ts

@@ -44,6 +44,7 @@ import { RelayControllerModule } from '@/routes/relay/relay.controller.module';
 import { SubscriptionControllerModule } from '@/routes/subscriptions/subscription.module';
 import { LockingModule } from '@/routes/locking/locking.module';
 import { ZodErrorFilter } from '@/routes/common/filters/zod-error.filter';
+import { CacheControlInterceptor } from '@/routes/common/interceptors/cache-control.interceptor';
 
 @Module({})
 export class AppModule implements NestModule {
@@ -116,6 +117,10 @@ export class AppModule implements NestModule {
           provide: APP_INTERCEPTOR,
           useClass: RouteLoggerInterceptor,
         },
+        {
+          provide: APP_INTERCEPTOR,
+          useClass: CacheControlInterceptor,
+        },
         {
           provide: APP_FILTER,
           useClass: GlobalErrorFilter,

src/routes/common/interceptors/cache-control.interceptor.spec.ts

@@ -0,0 +1,37 @@
+import {
+  Controller,
+  Get,
+  INestApplication,
+  UseInterceptors,
+} from '@nestjs/common';
+import { CacheControlInterceptor } from '@/routes/common/interceptors/cache-control.interceptor';
+import { Test } from '@nestjs/testing';
+import * as request from 'supertest';
+
+@Controller()
+@UseInterceptors(CacheControlInterceptor)
+class TestController {
+  @Get()
+  test(): void {
+    return;
+  }
+}
+
+describe('CacheControlInterceptor tests', () => {
+  let app: INestApplication;
+
+  beforeEach(async () => {
+    const module = await Test.createTestingModule({
+      controllers: [TestController],
+    }).compile();
+
+    app = module.createNestApplication();
+    await app.init();
+  });
+
+  it('should set the Cache-Control header to no-cache', () => {
+    return request(app.getHttpServer())
+      .get('/')
+      .expect('Cache-Control', 'no-cache');
+  });
+});

src/routes/common/interceptors/cache-control.interceptor.ts

@@ -0,0 +1,25 @@
+import {
+  CallHandler,
+  ExecutionContext,
+  Injectable,
+  NestInterceptor,
+} from '@nestjs/common';
+import { Observable, tap } from 'rxjs';
+
+/**
+ * This interceptor can be used to set the `Cache-Control` header to `no-cache`.
+ */
+@Injectable()
+export class CacheControlInterceptor implements NestInterceptor {
+  intercept(
+    context: ExecutionContext,
+    next: CallHandler,
+  ): Observable<unknown> | Promise<Observable<unknown>> {
+    return next.handle().pipe(
+      tap(() => {
+        const response = context.switchToHttp().getResponse();
+        response.header('Cache-Control', 'no-cache');
+      }),
+    );
+  }
+}

src/routes/relay/relay.legacy.controller.ts

@@ -1,42 +1,35 @@
 import { RelayLegacyDto } from '@/routes/relay/entities/relay.legacy.dto.entity';
 import { RelayLegacyDtoValidationPipe } from '@/routes/relay/pipes/relay.legacy.validation.pipe';
 import {
+  Body,
   Controller,
-  Post,
   Get,
   HttpStatus,
-  Res,
   Param,
-  Body,
+  Post,
+  Redirect,
 } from '@nestjs/common';
-import { Response } from 'express';
 
 @Controller({
   version: '1',
   path: 'relay',
 })
 export class RelayLegacyController {
   @Post()
+  @Redirect(undefined, HttpStatus.PERMANENT_REDIRECT)
   relay(
     @Body(RelayLegacyDtoValidationPipe)
     relayLegacyDto: RelayLegacyDto,
-    @Res() res: Response,
-  ): void {
-    res.redirect(
-      HttpStatus.PERMANENT_REDIRECT,
-      `/v1/chains/${relayLegacyDto.chainId}/relay`,
-    );
+  ): { url: string } {
+    return { url: `/v1/chains/${relayLegacyDto.chainId}/relay` };
   }
 
   @Get('/:chainId/:safeAddress')
+  @Redirect(undefined, HttpStatus.MOVED_PERMANENTLY)
   getRelaysRemaining(
     @Param('chainId') chainId: string,
     @Param('safeAddress') safeAddress: string,
-    @Res() res: Response,
-  ): void {
-    res.redirect(
-      HttpStatus.MOVED_PERMANENTLY,
-      `/v1/chains/${chainId}/relay/${safeAddress}`,
-    );
+  ): { url: string } {
+    return { url: `/v1/chains/${chainId}/relay/${safeAddress}` };
   }
 }