Merge branch '6610-missing-dkim-public' into 'develop'

Resolve "manually added DKIM key creates empty DNS RR"

Closes #6610

See merge request ispconfig/ispconfig3!1830

Author: Till Brehm

interface/web/mail/mail_domain_edit.php

@@ -331,6 +331,11 @@ function onSubmit() {
 			$this->dataRecord["domain"] = strtolower($this->dataRecord["domain"]);
 		}
 
+		// Extract the dkim public key if not submitted.
+		if (!empty($this->dataRecord['dkim_private']) && empty( $this->dataRecord['dkim_public']) && function_exists('openssl_pkey_get_details')) {
+			$this->dataRecord['dkim_public'] = openssl_pkey_get_details(openssl_pkey_get_private($this->dataRecord['dkim_private']))['key'];
+		}
+
 		//* server_id must be > 0
 		if(isset($this->dataRecord["server_id"]) && $this->dataRecord["server_id"] < 1) $app->tform->errorMessage .= $app->lng("server_id_0_error_txt");