feat(packages): add standalone auth and payment

packages/auth/src/marketplace-context.ts

@@ -0,0 +1,28 @@
+import { HttpHeaders } from '@angular/common/http';
+import { Injectable, inject } from '@angular/core';
+import { MARKETPLACES_AUTH_CONFIG } from './config';
+
+export const MARKETPLACE_DOMAIN_HEADER = 'X-Marketplace-Domain';
+
+export function normalizeMarketplaceDomain(domain: string): string {
+  return domain.trim().toLowerCase().replace(/\.$/, '');
+}
+
+@Injectable({ providedIn: 'root' })
+export class AuthMarketplaceContext {
+  private readonly config = inject(MARKETPLACES_AUTH_CONFIG);
+
+  domain(): string {
+    const configured = this.config.marketplaceDomain;
+    const domain = typeof configured === 'function'
+      ? configured()
+      : configured ?? (typeof location === 'undefined' ? '' : location.hostname);
+    return normalizeMarketplaceDomain(domain);
+  }
+
+  headers(extra?: Record<string, string>): HttpHeaders {
+    const domain = this.domain();
+    if (!domain) throw new Error('Marketplace domain cannot be resolved');
+    return new HttpHeaders({ [MARKETPLACE_DOMAIN_HEADER]: domain, ...extra });
+  }
+}