Add migration code for Dogfood to module. (#9648)

# Checklist for submitter
Closes https://github.com/fleetdm/fleet/issues/9385

If some of the following don't apply, delete the relevant line.

- [ ] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
See [Changes
files](https://fleetdm.com/docs/contributing/committing-changes#changes-files)
for more information.
- [ ] Documented any API changes (docs/Using-Fleet/REST-API.md or
docs/Contributing/API-for-contributors.md)
- [ ] Documented any permissions changes
- [ ] Input data is properly validated, `SELECT *` is avoided, SQL
injection is prevented (using placeholders for values in statements)
- [ ] Added support on fleet's osquery simulator `cmd/osquery-perf` for
new osquery data ingestion features.
- [ ] Added/updated tests
- [ ] Manual QA for all new/changed functionality
  - For Orbit and Fleet Desktop changes:
- [ ] Manual QA must be performed in the three main OSs, macOS, Windows
and Linux.
- [ ] Auto-update manual QA, from released version of component to new
version (see [tools/tuf/test](../tools/tuf/test/README.md)).

terraform/.header.md

@@ -8,6 +8,28 @@ The following is the module layout so you can navigate to the module that you wa
         * BYO-database (use this if you want to use an existing database and cache node)
             * BYO-ECS (use this if you want to bring your own everything but Fleet ECS services)
 
+# Migrating from existing Dogfood code
+The below code describes how to migrate from existing Dogfood code
+
+```hcl
+moved {
+  from = module.vpc
+  to   = module.main.module.vpc
+}
+
+moved {
+  from = module.aurora_mysql
+  to = module.main.module.byo-vpc.module.rds
+}
+
+moved {
+  from = aws_elasticache_replication_group.default
+  to = module.main.module.byo-vpc.module.redis.aws_elasticache_replication_group.default
+}
+```
+
+This focuses on the resources that are "heavy" or store data. Note that the ALB cannot be moved like this because Dogfood uses the `aws_alb` resource and the module uses the `aws_lb` resource. The resources are aliases of eachother, but Terraform can't recognize that.
+
 # How to improve this module
 If this module somehow doesn't fit your needs, feel free to contact us by
 opening a ticket, or contacting your contact at Fleet. Our goal is to make this module

terraform/README.md

@@ -8,6 +8,28 @@ The following is the module layout so you can navigate to the module that you wa
         * BYO-database (use this if you want to use an existing database and cache node)
             * BYO-ECS (use this if you want to bring your own everything but Fleet ECS services)
 
+# Migrating from existing Dogfood code
+The below code describes how to migrate from existing Dogfood code
+
+```hcl
+moved {
+  from = module.vpc
+  to   = module.main.module.vpc
+}
+
+moved {
+  from = module.aurora_mysql
+  to = module.main.module.byo-vpc.module.rds
+}
+
+moved {
+  from = aws_elasticache_replication_group.default
+  to = module.main.module.byo-vpc.module.redis.aws_elasticache_replication_group.default
+}
+```
+
+This focuses on the resources that are "heavy" or store data. Note that the ALB cannot be moved like this because Dogfood uses the `aws_alb` resource and the module uses the `aws_lb` resource. The resources are aliases of eachother, but Terraform can't recognize that.
+
 # How to improve this module
 If this module somehow doesn't fit your needs, feel free to contact us by
 opening a ticket, or contacting your contact at Fleet. Our goal is to make this module