Add send_only_mailserver role and deploy Send-Only-Mailserver with it

Co-authored-by: yuri <yuri@nekover.se>

playbooks/roles/send_only_mail_server/meta/argument_specs.yaml

@@ -0,0 +1,31 @@
+argument_specs:
+  main:
+    options:
+      send_only_mail_server__mail_server_fqdn:
+        description: The FQDN of the mail server host itself.
+        type: str
+        required: true
+      send_only_mail_server__mail_server_fqdn_zone:
+        description: >
+          The DNS zone on the BIND 9 server for records for the mail server host
+          FQDN.
+        type: str
+        required: true
+      send_only_mail_server__mail_domains:
+        description: The domains the mail server should send mails for.
+        type: list
+        elements: dict
+        required: true
+        options:
+          name:
+            description: The domain name.
+            type: str
+            required: true
+          zone:
+            description: The DNS zone on the BIND 9 server.
+            type: str
+            required: true
+      send_only_mail_server__bind_9_host:
+        description: The machine running BIND 9 to deploy DNS records via.
+        type: str
+        required: true

playbooks/roles/send_only_mail_server/meta/main.yaml

@@ -0,0 +1,7 @@
+dependencies: # noqa meta-no-info
+  - role: distribution_check
+    vars:
+      distribution_check__supported_distributions:
+        - name: Debian
+          versions:
+            - "11"