nginx(role): use better naming, wording and file structure

roles/nginx/tasks/main/01_validate_config_names.yaml

@@ -0,0 +1,7 @@
+- name: Ensure that the given configuration names are valid
+  ansible.builtin.fail:
+    msg: "You used one of the reserved configuration names: '{{ item.name }}'."
+  when: item.name == "tls"
+        or item.name == "redirect"
+        or item.name == "logging"
+  loop: "{{ nginx__configurations }}"