Add an $LTI{v1p3}{OverrideSiteProtocolDomain} LTI 1.3 configuration…

… variable.

This is similar to the same named LTI 1.1 configuration variable.  It
should be set to a URL, and the protocol and domain name in the URL
replace the protocol and domain of the server as seen by the webwork2
app that is used for the issuer in the JWT sent to the LMS when
requesting an access token for grade passback.

conf/authen_LTI_1_3.conf.dist

@@ -103,6 +103,12 @@ $LTI{v1p3}{AccessTokenURL}  = '';
 $LTI{v1p3}{AccessTokenAUD}  = '';
 $LTI{v1p3}{AuthReqURL}      = '';
 
+# This allows you to declare the protocol and domain of the issuer used in the JWT that is sent
+# when an access token is requested for grade passback from the LMS. These will replace the
+# protocol and domain in the root url for this server.
+$LTI{v1p1}{OverrideSiteProtocolDomain} = '';
+#$LTI{v1p1}{OverrideSiteProtocolDomain} = 'https://vmwebwork42.myschool.edu';
+
 # In the process of LTI 1.3 authentication a request is sent to the LMS in response to its
 # request.  State and nonce values are sent with this request, and those values must be verified
 # in the next response from the LMS.  These values are saved in the database so that they will

lib/WeBWorK/Authen/LTIAdvantage/SubmitGrade.pm

@@ -134,11 +134,21 @@ async sub get_access_token ($self) {
 		return;
 	}
 
+	# The url of the request is used for the issuer by default. This
+	# can be overriden by the OverrideSiteProtocolDomain setting.
+	my $iss = $c->url_for('root')->to_abs;
+	if ($ce->{LTI}{v1p3}{OverrideSiteProtocolDomain}) {
+		my $override = Mojo::URL->new($ce->{LTI}{v1p3}{OverrideSiteProtocolDomain});
+		$iss->scheme($override->scheme);
+		$iss->host($override->host);
+	}
+	$c->log->info($iss);
+
 	my $jwt = eval {
 		encode_jwt(
 			payload => {
 				aud => $ce->{LTI}{v1p3}{AccessTokenAUD},
-				iss => $c->url_for('root')->to_abs->to_string,
+				iss => $iss,
 				sub => $ce->{LTI}{v1p3}{ClientID},
 				jti => $private_key->{kid}
 			},