Allow skipping SSH key and config generation

Add when conditions to skip SSH key generation and borgmatic config
creation when corresponding variables are empty. This allows users
to install only borg/borgmatic without configuring them.

Closes #188 #152

Co-Authored-By: Leonidas Avdelas <avdelasleonidas@gmail.com>

tasks/03_create_key.yml

@@ -17,13 +17,16 @@
         owner: "{{ borg_user }}"
         group: "{{ borg_group }}"
         comment: "{{ borg_ssh_key_comment }}"
+      when: borg_ssh_key_file_path is defined and borg_ssh_key_file_path | length > 0
 
     - name: Read SSH key
       ansible.builtin.slurp:
         src: "{{ borg_ssh_key_file_path }}.pub"
       register: backup_local_ssh_key
+      when: borg_ssh_key_file_path is defined and borg_ssh_key_file_path | length > 0
 
     - name: Print key
       ansible.builtin.debug:
         msg: "The generated key is: {{ backup_local_ssh_key['content'] | b64decode }}"
+      when: borg_ssh_key_file_path is defined and borg_ssh_key_file_path | length > 0
 ...

tasks/05_configure.yml

@@ -1,5 +1,6 @@
 ---
 - name: Add Borgmatic config file
+  when: borgmatic_config_name is defined and borgmatic_config_name | length > 0
   block:
     - name: Get Borgmatic version
       ansible.builtin.command: borgmatic --version