Automate Lambda image switchover

If the Lambda is configured to use the image tagged latest, I think it
will automatically update on push. I discovered that from running the
added command. Therefore I think adding this bit isn't necessary, but
hey, it can't hurt.

Lifecycle rules can be configured in ECR to clean up old images, so that
should cover that. Deletion does not therefore need to be automated.

build_deploy_lambda.sh

@@ -3,9 +3,9 @@
 set -e
 
 docker build --target execute_lambda --tag notifier:execute_lambda --tag 288611151503.dkr.ecr.eu-west-2.amazonaws.com/wikidot_notifier:latest --provenance false .
+
 aws ecr get-login-password --region eu-west-2 --profile notifier | docker login --username AWS --password-stdin 288611151503.dkr.ecr.eu-west-2.amazonaws.com
+
 docker push 288611151503.dkr.ecr.eu-west-2.amazonaws.com/wikidot_notifier:latest
 
-echo "Next steps:"
-echo "In Lambda, re-select the new image as the Lambda image"
-echo "In ECR, delete old untagged images"
+aws lambda update-function-code --function-name WikidotNotifier --image-uri 288611151503.dkr.ecr.eu-west-2.amazonaws.com/wikidot_notifier:latest --region eu-west-2 --profile notifier