Fix handling custom date fields with value {now}

The issue should be created with custom field set to today's date,
but it gets created with literal string {now} that can't be displayed
later. The fix would be resolve {now} at reporting time and fix display
of existing issues by showing empty date.

This applies to issues created via web ui when the date field is not
visible on reporting page.

Fixes #23594

bug_report.php

@@ -220,7 +220,8 @@
 	}
 
 	$t_def = custom_field_get_definition( $t_id );
-	if( !custom_field_set_value( $t_id, $t_bug_id, gpc_get_custom_field( 'custom_field_' . $t_id, $t_def['type'], $t_def['default_value'] ), false ) ) {
+	if( !custom_field_set_value( $t_id, $t_bug_id, gpc_get_custom_field( 'custom_field_' . $t_id,
+	    $t_def['type'], custom_field_default_to_value( $t_def['default_value'], $t_def['type'] ), false ) ) ) {
 		error_parameters( lang_get_defaulted( custom_field_get_field( $t_id, 'name' ) ) );
 		trigger_error( ERROR_CUSTOM_FIELD_INVALID_VALUE, ERROR );
 	}

core/cfdefs/cfdef_standard.php

@@ -347,6 +347,13 @@ function cfdef_prepare_email_value( $p_value ) {
  */
 function cfdef_prepare_date_value( $p_value ) {
 	if( $p_value != null ) {
+		# There is a bug where default dates were being saved as '{now}' rather
+		# than being evaluated at creation time, so replace them with empty string.
+		$t_value_length = strlen( $p_value );
+		if( $t_value_length >= 3 && $p_value[0] == '{' && $p_value[$t_value_length - 1] == '}' ) {
+			return '';
+		}
+
 		return date( config_get( 'short_date_format' ), $p_value );
 	}
 }