Refactor resource configuration:

- Introduce new resource_filter plugin (mandatory hard_default, auto entity_name fallback)
- Replace get_app_conf calls with resource_filter in resource.yml.j2
- Add WEBSERVER_CPUS_EFFECTIVE, WEBSERVER_WORKER_PROCESSES, WEBSERVER_WORKER_CONNECTIONS to 05_webserver.yml
- Update Nginx templates (sys-svc-webserver, web-app-magento, web-app-nextcloud) to use new vars
- Extend svc-prx-openresty config with cpus/mem limits
- Add unit tests for resource_filter

Details: https://chatgpt.com/share/68d3a493-9a5c-800f-8cd2-bd2e7a3e3fda

group_vars/all/05_webserver.yml

@@ -29,4 +29,31 @@ NGINX:
       IMAGE:          "/tmp/cache_nginx_image/"             # Directory which nginx uses to cache images
   USER:               "http"                                # Default nginx user in ArchLinux
 
+# Effective CPUs (float) across proxy and the current app
+WEBSERVER_CPUS_EFFECTIVE: >-
+  {{
+    [
+      (applications | resource_filter('svc-prx-openresty', 'cpus', service_name | default(''), RESOURCE_CPUS)) | float,
+      (applications | resource_filter(application_id,           'cpus', service_name | default(''), RESOURCE_CPUS)) | float
+    ] | min
+  }}
+
+# Nginx requires an integer for worker_processes:
+# - if cpus < 1 → 1
+# - else → floor to int
+WEBSERVER_WORKER_PROCESSES: >-
+  {{
+    1 if WEBSERVER_CPUS_EFFECTIVE < 1
+    else (WEBSERVER_CPUS_EFFECTIVE | int)
+  }}
+
+# worker_connections from pids_limit (use the smaller one), with correct key/defaults
+WEBSERVER_WORKER_CONNECTIONS: >-
+  {{
+    [
+      (applications | resource_filter('svc-prx-openresty', 'pids_limit', service_name | default(''), RESOURCE_PIDS_LIMIT)) | int,
+      (applications | resource_filter(application_id,           'pids_limit', service_name | default(''), RESOURCE_PIDS_LIMIT)) | int
+    ] | min
+  }}
+
 # @todo It propably makes sense to distinguish between target and source mount path, so that the config files can be stored in the openresty volumes folder