feat(multitenancy): Add TenantHeaderMiddleware to support centralized API with tenant switching

- Implemented TenantHeaderMiddleware to switch the database tenant schema based on the 'X-Business-Subdomain' request header.
- This allows API requests directed to the centralized 'api' subdomain (e.g., api.lvh.me) to correctly access tenant-specific data when the header is present.
- Registered the middleware in multitenancy settings after TenantMainMiddleware.

smoothschedule/config/settings/multitenancy.py

@@ -94,6 +94,7 @@ MIDDLEWARE = [
 
     # 1. Tenant resolution
     'django_tenants.middleware.main.TenantMainMiddleware',
+    'core.middleware.TenantHeaderMiddleware', # Support tenant switching via header
 
     # 2. Security middleware
     'django.middleware.security.SecurityMiddleware',

smoothschedule/core/middleware.py

@@ -8,11 +8,35 @@ import json
 from django.utils.deprecation import MiddlewareMixin
 from django.utils import timezone
 from django.db import connection
+from django_tenants.utils import get_tenant_model
 
 logger = logging.getLogger('smoothschedule.security.masquerade')
 sandbox_logger = logging.getLogger('smoothschedule.sandbox')
 
 
+class TenantHeaderMiddleware(MiddlewareMixin):
+    """
+    Middleware to switch tenant based on 'X-Business-Subdomain' header.
+    Allows centralized API domain (e.g., api.smoothschedule.com) to serve tenant-specific data.
+    Must be placed AFTER TenantMainMiddleware.
+    """
+    def process_request(self, request):
+        # Check for header
+        subdomain = request.META.get('HTTP_X_BUSINESS_SUBDOMAIN')
+        if subdomain:
+            Tenant = get_tenant_model()
+            try:
+                tenant = Tenant.objects.get(schema_name=subdomain)
+                # Only switch if different from current tenant (which might be 'public')
+                if request.tenant.schema_name != tenant.schema_name:
+                    request.tenant = tenant
+                    connection.set_tenant(request.tenant)
+                    # sandbox_logger.debug(f"Switched to tenant '{subdomain}' via header")
+            except Tenant.DoesNotExist:
+                # Invalid subdomain in header - ignore or could raise 400
+                pass
+
+
 class SandboxModeMiddleware(MiddlewareMixin):
     """
     Middleware to switch between live and sandbox schemas based on: