flatten the "playbooks" directory for better structure

Because of how Ansible local relative search paths work, the global
"files" and "templates" directories need to be next to the playbooks.
However its not intuitive to look into the playbooks directory to find
the files and templates for a host.
Therefore flatten the playbooks directory to get rid of this confusing
structure.

Also see:
https://docs.ansible.com/ansible/latest/playbook_guide/playbook_pathing.html#resolving-local-relative-paths

roles/certbot/meta/argument_specs.yaml

@@ -0,0 +1,36 @@
+argument_specs:
+  main:
+    options:
+      certbot__version_spec:
+        description: >-
+          The version specification to use for installing the `certbot` package.
+          The provided version specification will be used like the following:
+          `cerbot={{ certbot__version_spec }}*`. This makes it possible to e.g.
+          specify until a minor version (like `1.3.`) and then have patch
+          versions be installed automatically (like `1.3.1` and so on).
+        type: str
+        required: true
+      certbot__acme_account_email_address:
+        description: The E-Mail address to give to certbot for the ACME account.
+        type: str
+        required: true
+      certbot__certificate_domains:
+        description: The domains for which to obtain a certificate.
+        type: list
+        elements: str
+        required: true
+      certbot__http_01_port:
+        description: |
+          The port number the bot listens on. Must be 80 if directly exposed to the internet.
+          Default is 31820 for the public-reverse-proxy setup.
+        type: str
+        required: false
+        default: 31820
+      certbot__new_cert_commands:
+        description: >-
+          A list of commands to execute after getting a new certificate.
+          Will be added into a bash script.
+        type: list
+        elements: str
+        required: false
+        default: [ ]

roles/certbot/meta/main.yaml

@@ -0,0 +1,9 @@
+---
+dependencies:
+  - role: distribution_check
+    vars:
+      distribution_check__distribution_support_spec:
+        - name: Debian
+          major_versions:
+            - 11
+            - 12