refactor: extract the duplicated certificate concatenation into a shared task file

Building chain.pem, fullchain.pem and all.pem was implemented seven times across three task files with
identical stat, awk and copy tasks. The blocks now include tasks/concatenate.yaml and pass the sources, the
destination and the mode, which removes about a hundred lines.

Two side effects come with it. Every source file is checked instead of only the foreign one, so a missing
file skips the block instead of letting awk fail. And the trailing newline of the result is kept, because
stdout_lines joined by a newline dropped it.

Co-authored-by: Copilot <copilot@github.com>

tasks/root_certificate_authority.yaml

@@ -38,31 +38,13 @@
   - fullchain.pem
 
 - name: Create file with private key and fullchain file of root Certificate Authority (CA)
-  block:
-  - name: Check if private key exists
-    ansible.builtin.stat:
-      path: "{{ certificate_authority_root_ca_path }}/privkey.pem"
-    register: _stat_result
-  - name: Concatenate private key and fullchain file of root Certificate Authority (CA)
-    vars:
-      _chain_files:
-      - "{{ certificate_authority_root_ca_path }}/privkey.pem"
-      - "{{ certificate_authority_root_ca_path }}/fullchain.pem"
-    ansible.builtin.command:
-      cmd: awk 1 {{ _chain_files | join(' ') }}
-    register: chain_content
-    changed_when: false
-    when: _stat_result.stat.exists is defined and
-          _stat_result.stat.exists
-  - name: Create concatenated file
-    ansible.builtin.copy:
-      content: "{{ chain_content.stdout_lines | join('\n') }}"
-      dest: "{{ certificate_authority_root_ca_path }}/all.pem"
-      owner: "root"
-      group: "root"
-      mode: "0600"
-    when: _stat_result.stat.exists is defined and
-          _stat_result.stat.exists
+  ansible.builtin.include_tasks: concatenate.yaml
+  vars:
+    _concat_sources:
+    - "{{ certificate_authority_root_ca_path }}/privkey.pem"
+    - "{{ certificate_authority_root_ca_path }}/fullchain.pem"
+    _concat_dest: "{{ certificate_authority_root_ca_path }}/all.pem"
+    _concat_mode: "0600"
 
 - name: Import certificate of root Certificate Authority (CA) into systems trust store
   vars: