services: mail: Deprecate 'dovecot-service' procedure.

* doc/guix.texi (Mail Services): Replace 'dovecot-service' with 'dovecot-service-type'.
* gnu/services/mail.scm (dovecot-service-type): Set default value.
(dovecot-service): Deprecate procedure.
* gnu/tests/mail.scm (%dovecot-os): Use dovecot-service-type.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -24709,9 +24709,10 @@ in the subsections below.
 
 @subsubheading Dovecot Service
 
-@deffn {Scheme Procedure} dovecot-service [#:config (dovecot-configuration)]
-Return a service that runs the Dovecot IMAP/POP3/LMTP mail server.
-@end deffn
+@defvar dovecot-service-type
+Type for the service that runs the Dovecot IMAP/POP3/LMTP mail server,
+whose value is a @code{<dovecot-configuration>} object.
+@end defvar
 
 By default, Dovecot does not need much configuration; the default
 configuration object created by @code{(dovecot-configuration)} will
@@ -24726,7 +24727,7 @@ For example, to specify that mail is located at @code{maildir~/.mail},
 one would instantiate the Dovecot service like this:
 
 @lisp
-(dovecot-service #:config
+(service dovecot-service-type
          (dovecot-configuration
            (mail-location "maildir:~/.mail")))
 @end lisp

gnu/services/mail.scm

@@ -35,6 +35,7 @@
   #:use-module (gnu packages admin)
   #:use-module (gnu packages dav)
   #:use-module (gnu packages tls)
+  #:use-module (guix deprecation)
   #:use-module (guix modules)
   #:use-module (guix records)
   #:use-module (guix packages)
@@ -42,7 +43,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 format)
   #:use-module (srfi srfi-1)
-  #:export (dovecot-service
+  #:export (dovecot-service  ; deprecated
             dovecot-service-type
             dovecot-configuration
             opaque-dovecot-configuration
@@ -1601,9 +1602,11 @@ greyed out, instead of only later giving \"not selectable\" popup error.
                        (service-extension activation-service-type
                                           %dovecot-activation)))
                 (description "Run Dovecot, a mail server that can run POP3,
-IMAP, and LMTP.")))
+IMAP, and LMTP.")
+                (default-value (dovecot-configuration))))
 
-(define* (dovecot-service #:key (config (dovecot-configuration)))
+(define-deprecated (dovecot-service #:key (config (dovecot-configuration)))
+  dovecot-service-type
   "Return a service that runs @command{dovecot}, a mail server that can run
 POP3, IMAP, and LMTP.  @var{config} should be a configuration object created
 by @code{dovecot-configuration}.  @var{config} may also be created by

gnu/tests/mail.scm

@@ -293,7 +293,7 @@ acl_check_data:
 (define %dovecot-os
   (simple-operating-system
    (service dhcp-client-service-type)
-   (dovecot-service #:config
+   (service dovecot-service-type
             (dovecot-configuration
              (disable-plaintext-auth? #f)
              (ssl? "no")