Remove more hardcoded matrix-postgres references

roles/custom/matrix-prometheus-postgres-exporter/tasks/main.yml

@@ -10,6 +10,9 @@
     - install-nginx-proxy
 
 - block:
+    - when: matrix_prometheus_postgres_exporter_enabled | bool
+      ansible.builtin.include_tasks: "{{ role_path }}/tasks/validate_config.yml"
+
     - when: matrix_prometheus_postgres_exporter_enabled | bool
       ansible.builtin.include_tasks: "{{ role_path }}/tasks/setup_install.yml"
   tags:

roles/custom/matrix-prometheus-postgres-exporter/tasks/validate_config.yml

@@ -0,0 +1,9 @@
+---
+
+- name: Fail if required prometheus-postgres-exporter settings not defined
+  ansible.builtin.fail:
+    msg: >
+      You need to define a required configuration setting (`{{ item }}`).
+  when: "vars[item] == ''"
+  with_items:
+    - matrix_prometheus_postgres_exporter_database_hostname