chore(portal): add non-composite indexes (#10396)

Why:

* Now that hard-delete has been rolled out, we need to make sure that
all cascade deletes are efficient. Some of the foreign key references
didn't have indexes but needed them.

Fixes #10393

elixir/apps/domain/priv/repo/migrations/20250919205908_add_non_composite_indexes_for_cascade_fks.exs

@@ -0,0 +1,49 @@
+defmodule Domain.Repo.Migrations.AddNonCompositeIndexesForCascadeFks do
+  use Ecto.Migration
+
+  @disable_ddl_transaction true
+
+  def change do
+    # Indexes for actor_groups table CASCADE foreign key
+    create_if_not_exists(index(:actor_groups, [:provider_id], concurrently: true))
+
+    # Indexes for auth_identities table CASCADE foreign keys
+    create_if_not_exists(index(:auth_identities, [:actor_id], concurrently: true))
+    create_if_not_exists(index(:auth_identities, [:provider_id], concurrently: true))
+
+    # Indexes for clients table CASCADE foreign keys
+    create_if_not_exists(index(:clients, [:actor_id], concurrently: true))
+    create_if_not_exists(index(:clients, [:identity_id], concurrently: true))
+
+    # Indexes for flows table CASCADE foreign keys
+    create_if_not_exists(index(:flows, [:actor_group_membership_id], concurrently: true))
+    create_if_not_exists(index(:flows, [:client_id], concurrently: true))
+    create_if_not_exists(index(:flows, [:gateway_id], concurrently: true))
+    create_if_not_exists(index(:flows, [:policy_id], concurrently: true))
+    create_if_not_exists(index(:flows, [:resource_id], concurrently: true))
+    create_if_not_exists(index(:flows, [:token_id], concurrently: true))
+
+    # Indexes for gateways table CASCADE foreign key
+    create_if_not_exists(index(:gateways, [:group_id], concurrently: true))
+
+    # Index for policies table CASCADE foreign key
+    create_if_not_exists(index(:policies, [:replaced_by_policy_id], concurrently: true))
+
+    # Indexes for relays table CASCADE foreign keys
+    create_if_not_exists(index(:relays, [:account_id], concurrently: true))
+    create_if_not_exists(index(:relays, [:group_id], concurrently: true))
+
+    # Index for resources table CASCADE foreign key
+    create_if_not_exists(index(:resources, [:replaced_by_resource_id], concurrently: true))
+
+    # Indexes for resource_connections table CASCADE foreign keys
+    create_if_not_exists(index(:resource_connections, [:resource_id], concurrently: true))
+    create_if_not_exists(index(:resource_connections, [:gateway_group_id], concurrently: true))
+
+    # Indexes for tokens table CASCADE foreign keys
+    create_if_not_exists(index(:tokens, [:relay_group_id], concurrently: true))
+    create_if_not_exists(index(:tokens, [:gateway_group_id], concurrently: true))
+    create_if_not_exists(index(:tokens, [:actor_id], concurrently: true))
+    create_if_not_exists(index(:tokens, [:identity_id], concurrently: true))
+  end
+end