feat(portal): real diploma file upload on the self-service page (refs #103)

Replaces the S-10a stub button with a labelled file input (accept application/pdf);
the component base64-encodes the chosen file client-side and posts it (with its name
and type) keyed by the reference, confirming on success and surfacing a retryable
failure. The upload button stays disabled until a file is chosen.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/self-service/src/app/registration/registration-page.html

@@ -19,11 +19,20 @@
               Het aanleveren van uw documenten is niet gelukt. Probeer het opnieuw.
             </p>
           }
+          <p utrecht-paragraph>Lever uw diploma aan (PDF).</p>
+          <label utrecht-form-label for="diploma">Diploma</label>
+          <input
+            id="diploma"
+            type="file"
+            accept="application/pdf"
+            [disabled]="providingDocuments()"
+            (change)="onFileSelected($event)"
+          />
           <button
             utrecht-button
             appearance="primary-action-button"
             type="button"
-            [disabled]="providingDocuments()"
+            [disabled]="providingDocuments() || !selectedFile()"
             (click)="provideDocuments()"
           >
             Documenten aanleveren

apps/self-service/src/app/registration/registration-page.ts

@@ -29,6 +29,7 @@ export class RegistrationPage {
   protected readonly providingDocuments = signal(false);
   protected readonly documentsProvided = signal(false);
   protected readonly provideDocumentsFailed = signal(false);
+  protected readonly selectedFile = signal<File | undefined>(undefined);
 
   submit(): void {
     this.submitting.set(true);
@@ -47,14 +48,34 @@ export class RegistrationPage {
     });
   }
 
-  provideDocuments(): void {
+  onFileSelected(event: Event): void {
+    const input = event.target as HTMLInputElement;
+    this.selectedFile.set(input.files?.[0] ?? undefined);
+  }
+
+  async provideDocuments(): Promise<void> {
     const reference = this.reference();
-    if (!reference) {
+    const file = this.selectedFile();
+    if (!reference || !file) {
       return;
     }
     this.providingDocuments.set(true);
     this.provideDocumentsFailed.set(false);
-    this.bff.postSelfServiceRegistrationsIdDocuments(reference).subscribe({
+    let contentBase64: string;
+    try {
+      contentBase64 = await readAsBase64(file);
+    } catch {
+      this.provideDocumentsFailed.set(true);
+      this.providingDocuments.set(false);
+      return;
+    }
+    this.bff
+      .postSelfServiceRegistrationsIdDocuments(reference, {
+        contentBase64,
+        fileName: file.name,
+        contentType: file.type || 'application/pdf',
+      })
+      .subscribe({
         next: () => {
           this.documentsProvided.set(true);
           this.providingDocuments.set(false);
@@ -87,3 +108,13 @@ export class RegistrationPage {
     });
   }
 }
+
+/** Read a file's bytes as a base64 string (without the `data:...;base64,` prefix). */
+function readAsBase64(file: File): Promise<string> {
+  return new Promise<string>((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onload = () => resolve(((reader.result as string) ?? '').split(',', 2)[1] ?? '');
+    reader.onerror = () => reject(reader.error ?? new Error('Could not read the file.'));
+    reader.readAsDataURL(file);
+  });
+}