feat: add PR preview deployments via Azure Static Web Apps

Closes #64

- Add apiBaseUrlInterceptor: prepends apiBaseUrl to /api/* requests,
  allowing the Angular app to call the production backend from a
  different origin in preview builds
- Add environment files: environment.ts (empty = same-origin, used in
  dev and prod) and environment.preview.ts (production App Service URL)
- Add preview build configuration in project.json with fileReplacements
  to swap in environment.preview.ts
- Add staticwebapp.config.json for SPA fallback routing in Azure SWA
- Add CORS policy in Program.cs allowing *.azurestaticapps.net origins
- Add preview.yml workflow: builds Angular with the preview config,
  deploys to Azure SWA on PR open/sync, closes staging env on PR close

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: chrisjwalk-bot

.github/workflows/preview.yml

@@ -0,0 +1,56 @@
+name: Preview
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, closed]
+    branches: [main]
+
+concurrency:
+  group: preview-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  deploy_preview:
+    if: github.event.action != 'closed'
+    name: Deploy Preview
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Build web app (preview)
+        run: pnpm nx build web-app --configuration preview
+
+      - name: Copy SWA routing config
+        run: cp apps/web-app/src/staticwebapp.config.json dist/apps/web-app/browser/
+
+      - name: Deploy to Azure Static Web Apps
+        uses: Azure/static-web-apps-deploy@v1
+        with:
+          azure_static_web_apps_api_token: ${{ secrets.AZURE_STATIC_WEB_APPS_API_TOKEN }}
+          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          action: upload
+          app_location: dist/apps/web-app/browser
+          skip_app_build: true
+
+  close_preview:
+    if: github.event.action == 'closed'
+    name: Close Preview
+    runs-on: ubuntu-latest
+    steps:
+      - name: Close staging environment
+        uses: Azure/static-web-apps-deploy@v1
+        with:
+          azure_static_web_apps_api_token: ${{ secrets.AZURE_STATIC_WEB_APPS_API_TOKEN }}
+          action: close

apps/api/Api/Program.cs

@@ -41,6 +41,17 @@
 
 builder.Services.AddControllers();
 
+builder.Services.AddCors(options =>
+  options.AddPolicy("SwaPreview", policy =>
+    policy
+      .SetIsOriginAllowed(origin =>
+        Uri.TryCreate(origin, UriKind.Absolute, out var uri)
+        && uri.Host.EndsWith(".azurestaticapps.net"))
+      .AllowAnyMethod()
+      .AllowAnyHeader()
+  )
+);
+
 var app = builder.Build();
 
 if (app.Environment.IsDevelopment())
@@ -85,6 +96,8 @@
 
 app.UseRouting();
 
+app.UseCors("SwaPreview");
+
 app.UseAuthorization();
 
 app.MapControllers();

apps/web-app/project.json

@@ -50,6 +50,15 @@
           "extractLicenses": false,
           "sourceMap": true,
           "namedChunks": true
+        },
+        "preview": {
+          "fileReplacements": [
+            {
+              "replace": "apps/web-app/src/environments/environment.ts",
+              "with": "apps/web-app/src/environments/environment.preview.ts"
+            }
+          ],
+          "outputHashing": "all"
         }
       },
       "defaultConfiguration": "production"

apps/web-app/src/app/api-base-url.interceptor.ts

@@ -0,0 +1,10 @@
+import { HttpInterceptorFn } from '@angular/common/http';
+
+import { environment } from '../environments/environment';
+
+export const apiBaseUrlInterceptor: HttpInterceptorFn = (req, next) => {
+  if (!environment.apiBaseUrl || !req.url.startsWith('/api')) {
+    return next(req);
+  }
+  return next(req.clone({ url: environment.apiBaseUrl + req.url }));
+};

apps/web-app/src/app/app.config.ts

@@ -19,12 +19,16 @@ import {
 import { provideServiceWorker } from '@angular/service-worker';
 import { authInterceptor } from '@myorg/auth';
 
+import { apiBaseUrlInterceptor } from './api-base-url.interceptor';
 import { routes } from './app.routes';
 
 export const appConfig: ApplicationConfig = {
   providers: [
     provideZonelessChangeDetection(),
-    provideHttpClient(withFetch(), withInterceptors([authInterceptor])),
+    provideHttpClient(
+      withFetch(),
+      withInterceptors([apiBaseUrlInterceptor, authInterceptor]),
+    ),
     provideRouter(
       routes,
       withComponentInputBinding(),

apps/web-app/src/environments/environment.preview.ts

@@ -0,0 +1,3 @@
+export const environment = {
+  apiBaseUrl: 'https://angularclinetcorengrxstarter.azurewebsites.net',
+};

apps/web-app/src/environments/environment.ts

@@ -0,0 +1,3 @@
+export const environment = {
+  apiBaseUrl: '',
+};

apps/web-app/src/staticwebapp.config.json

@@ -0,0 +1,6 @@
+{
+  "navigationFallback": {
+    "rewrite": "/index.html",
+    "exclude": ["/*.{css,js,png,gif,ico,jpg,svg,webmanifest,woff,woff2,txt}"]
+  }
+}