feat: add support for Dovecot IMAP/POP3 configuration

Introduces functionality to install and configure Dovecot alongside Postfix to provide IMAP/POP3 services.

Changes include:
- Added tasks to install Dovecot packages (core, imapd, pop3d, lmtpd).
- Added templates for main configuration and conf.d files (auth, master, ssl, mail).
- Defined default variables for protocols, SSL settings, and Maildir location.
- Enabled Postfix SASL and LMTP integration options.
- Added a handler to restart the Dovecot service.
- Updated README.md with the new configuration variables and usage instructions.

defaults/main.yml

@@ -34,4 +34,28 @@ postfix_relayhost: ""
 # Optional credentials for the relayhost. If these are defined,
 # SASL authentication will be automatically configured.
 # postfix_relayhost_user: "apikey"
-# postfix_relayhost_password: "YourVeryLongAndComplexApiKey"
+# postfix_relayhost_password: "YourVeryLongAndComplexApiKey"
+
+# --- Dovecot Configuration ---
+
+# Whether to install and configure Dovecot
+dovecot_enabled: true
+
+# Protocols to enable (imap, pop3, lmtp)
+dovecot_protocols: "imap pop3 lmtp"
+
+# Mail storage location. Using Maildir in the user's home directory.
+dovecot_mail_location: "maildir:~/Maildir"
+
+# SSL/TLS configuration
+# Use 'yes', 'no' or 'required'. 'required' is recommended for production.
+dovecot_ssl: "yes"
+dovecot_ssl_cert: "</etc/ssl/certs/ssl-cert-snakeoil.pem"
+dovecot_ssl_key: "</etc/ssl/private/ssl-cert-snakeoil.key"
+
+# Authentication mechanisms
+dovecot_auth_mechanisms: "plain login"
+
+# Postfix integration
+dovecot_postfix_sasl_enable: true
+dovecot_postfix_lmtp_enable: true