Add prerequisite steps to docs/sns-per-form-topic-routing.md

docs/sns-per-form-topic-routing.md

@@ -4,6 +4,44 @@ By default, all form submissions are published to a single global SNS topic conf
 
 When a form is submitted, the runner always publishes to the global topic. If the submitted form's ID is present in the per-form topic map, the exact same payload is also published to the configured topic for that form.
 
+## Pre-requisites
+
+Before any submission messages can be sent on a per-form basis, there are some infrastructure requirements that need to be done between the team that owns the form and the Defra Forms team.
+
+The Defra Forms team is responsible for creating and owning the SNS Topic.
+The service that owns the form is responsible for creating and owning the SQS Queue where the submissions will be sent and the subscription to the queue.
+
+Follow these CDP [instructions](https://portal.cdp-int.defra.cloud/documentation/how-to/sqs-sns.md#sns-sqs-creation-and-subscription-at-the-same-time-) to create all three at the same time.
+
+Follow this example below and use
+
+- the SNS Topic naming convention `forms_runner_submission_events_tenant_${owning_service_name}_${form_name}`
+- the SQS Queue naming convention `${owning_service_name}-${form_name}-form`
+
+```
+Hello CDP Support :wave: Please can I request an SNS/SQS creation and subscription with the following details:
+
+SQS QUEUE CREATION
+
+sqs_queue_name - epr-laps-feedback-form
+owning_service - epr-laps
+queue_type – Standard
+
+SNS TOPIC CREATION
+
+sns_topic_name - forms_runner_submission_events_tenant_erp_laps_feedback
+owning_service - forms-runner
+topic_type – Standard
+
+SNS/SQS SUBSCRIPTION CREATION
+
+owning_service - epr-laps
+sqs_queue_name_subscribing - epr-laps-feedback-form
+sns_topic_name_to_subscribe_to - forms_runner_submission_events_tenant_erp_laps_feedback
+
+Thank you
+```
+
 ## Configuration
 
 Set the `SNS_FORM_TOPIC_ARN_MAP` environment variable to a JSON object that maps form IDs to SNS topic ARNs. Environment variables are managed in the [cdp-app-config](https://github.com/defra/cdp-app-config) repository.