add postgres exporter

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

roles/postgres_exporter/tasks/get_version.yml

@@ -0,0 +1,18 @@
+---
+- name: Determine latest GitHub release (local)
+  delegate_to: localhost
+  ansible.builtin.uri:
+    url: "https://api.github.com/repos/{{ repository }}/releases/{{ version }}"
+    body_format: json
+  register: _github_release
+  until: _github_release.status == 200
+  retries: 3
+
+- name: Set version
+  ansible.builtin.set_fact:
+    tag: "{{ _github_release.json.tag_name
+      | regex_replace('^v?([0-9\\.]+)$', '\\1') }}"
+
+- name: Set download_url
+  ansible.builtin.set_fact:
+    download_url: "https://github.com/{{ repository }}/releases/download/v{{ tag }}/{{ bin_name }}-{{ tag }}.linux-{{ go_arch }}.tar.gz"