Update README

projects/email_alert_notifications/README.md

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+# Email Alert Notifications
 
+This project sets up an S3 bucket and a Lambda that parses files,
+extracts `data-govuk-request-id` and renames the file accordingly as
+either:
+
+    travel-advice-alerts/<data-govuk-request-id>.msg
+
+or if the file doesn't contain a `data-govuk-request-id`
+
+    no-request-id/<uuid>.msg
+
+## Manual Steps
+
+There are some manual steps required for this 'app'.
+
+* An SES domain with a RuleSet containing an action that writes to the S3
+bucket (`govuk-email-alert-notifications`). An address on this domain will be
+subscribed to all of the travel advice country alerts
+* An S3 event configured to execute the lambda (`rename_email_files_with_request_id`)
+on the `ObjectCreated` `Put` event for the bucket
+
+Terraform v0.6.14 doesn't support S3 event sources but support is in
+`master` and can be added to the project when released.
+
+## Updating the Lambda
+
+The lambda source is
+[here](resources/rename_email_files_with_request_id.py) 
+The [zip file](resources/) must be recreated 
+after any edits to the source as it is the zip file that is deployed to
+AWS.