feat(server): Option to configure SMTPS transport (#22833)

* feat(server): Option to configure SMTPS transport

This commit adds a boolean option in the SMTP transport configuration to
enable the so-called "secure" mode. What it does is use SMTP over TLS
instead of relying on the more common STARTTLS option over plain SMTP.

* Add missing field in dto

* Add missing field

* Use a switch instead of text field

* Add field in spec

* chore: regen open-api

---------

Co-authored-by: Jason Rasmussen <jason@rasm.me>

server/src/dtos/system-config.dto.ts

@@ -463,6 +463,9 @@ class SystemConfigSmtpTransportDto {
   @Max(65_535)
   port!: number;
 
+  @ValidateBoolean()
+  secure!: boolean;
+
   @IsString()
   username!: string;