OZG-6620 fix observable subscription

alfa-client/libs/postfach/src/lib/postfach-mail-form/postfach-mail.formservice.spec.ts

@@ -100,7 +100,8 @@ describe('PostfachMailFormservice', () => {
     it('should init mail body with signatur', () => {
       formService.initMailBody();
 
-      const mailBodyValue = formService.form.get(PostfachMailFormservice.FIELD_MAIL_BODY)?.value;
+      const mailBodyValue = formService.form.get(PostfachMailFormservice.FIELD_MAIL_BODY).value;
+
       expect(mailBodyValue).toBe(postfachSettings.signatur);
     });
   });

alfa-client/libs/postfach/src/lib/postfach-mail-form/postfach-mail.formservice.ts

@@ -32,7 +32,7 @@ import {
   UntypedFormGroup,
 } from '@angular/forms';
 import { ReplyOption } from 'libs/postfach-shared/src/lib/postfach.model';
-import { Observable, take } from 'rxjs';
+import { Observable, Subscription } from 'rxjs';
 
 @Injectable()
 export class PostfachMailFormservice extends AbstractFormService {
@@ -43,6 +43,8 @@ export class PostfachMailFormservice extends AbstractFormService {
   static readonly FIELD_REPLY_OPTION = 'replyOption';
   static readonly FIELD_ATTACHMENTS = 'attachments';
 
+  private loadPostfachSettingsSubscription: Subscription;
+
   constructor(
     formBuilder: UntypedFormBuilder,
     private postfachService: PostfachService,
@@ -61,12 +63,12 @@ export class PostfachMailFormservice extends AbstractFormService {
   }
 
   public initMailBody(): void {
-    this.postfachService
+    this.loadPostfachSettingsSubscription = this.postfachService
       .getSettings()
-      .pipe(take(1))
-      .subscribe((settings: PostfachSettings) =>
-        this.form.get(PostfachMailFormservice.FIELD_MAIL_BODY)?.setValue(settings.signatur),
-      );
+      .subscribe((settings: PostfachSettings) => {
+        this.form.get(PostfachMailFormservice.FIELD_MAIL_BODY)?.setValue(settings.signatur);
+        this.loadPostfachSettingsSubscription.unsubscribe();
+      });
   }
 
   protected getPathPrefix(): string {