Be able to test /login/sso/redirect in Complement (#17986)

Be able to test `/login/sso/redirect` in Complement

Spawning from
element-hq/sbg#421 (comment) where
we have a proxy that intercepts responses to
`/_matrix/client/v3/login/sso/redirect(/{idpId})` in order to upgrade
them to use OAuth 2.0 Pushed Authorization Requests (PAR). We have some
Complement tests in that codebase that go over this flow and these
changes are required [in order for the URL's to line
up](https://github.com/element-hq/synapse/blob/d648c8ce3f4cbf61191b9f5302e405f7b0288677/synapse/rest/client/login.py#L652-L673).

changelog.d/17986.misc

@@ -0,0 +1 @@
+Fix Docker and Complement config to be able to use `public_baseurl`.

docker/complement/conf/workers-shared-extra.yaml.j2

@@ -7,6 +7,7 @@
 #}
 
 ## Server ##
+public_baseurl: http://127.0.0.1:8008/
 report_stats: False
 trusted_key_servers: []
 enable_registration: true

docker/conf-workers/nginx.conf.j2

@@ -42,6 +42,6 @@ server {
 {% endif %}
         proxy_set_header X-Forwarded-For $remote_addr;
         proxy_set_header X-Forwarded-Proto $scheme;
-        proxy_set_header Host $host;
+        proxy_set_header Host $host:$server_port;
     }
 }

scripts-dev/complement.sh

@@ -195,6 +195,10 @@ if [ -z "$skip_docker_build" ]; then
         # Build the unified Complement image (from the worker Synapse image we just built).
         echo_if_github "::group::Build Docker image: complement/Dockerfile"
         $CONTAINER_RUNTIME build -t complement-synapse \
+            `# This is the tag we end up pushing to the registry (see` \
+            `# .github/workflows/push_complement_image.yml) so let's just label it now` \
+            `# so people can reference it by the same name locally.` \
+            -t ghcr.io/element-hq/synapse/complement-synapse \
             -f "docker/complement/Dockerfile" "docker/complement"
         echo_if_github "::endgroup::"
 

synapse/config/logger.py

@@ -360,5 +360,6 @@ def setup_logging(
         "Licensed under the AGPL 3.0 license. Website: https://github.com/element-hq/synapse"
     )
     logging.info("Server hostname: %s", config.server.server_name)
+    logging.info("Public Base URL: %s", config.server.public_baseurl)
     logging.info("Instance name: %s", hs.get_instance_name())
     logging.info("Twisted reactor: %s", type(reactor).__name__)