add foreign key to seen_sources.sql

deployment/hasura/metadata/databases/tables/ui/seen_sources.yaml

@@ -3,6 +3,12 @@ table:
   schema: ui
 configuration:
   custom_name: "seen_sources"
+object_relationships:
+  - name: external_source
+    using:
+      foreign_key_constraint_on:
+        - source_key
+        - derivation_group_name
 select_permissions:
   - role: aerie_admin
     permission:

deployment/postgres-init-db/sql/tables/ui/seen_sources.sql

@@ -3,13 +3,17 @@ create table ui.seen_sources
     username text not null,
     external_source_name text not null,
     derivation_group text not null,
-    external_source_type text not null, -- included for ease of filtering
+    external_source_type text not null, -- included for ease of filtering in the UI
 
     constraint seen_sources_pkey
       primary key (username, external_source_name, derivation_group),
     constraint seen_sources_references_user
       foreign key (username)
       references permissions.users (username) match simple
+      on delete cascade,
+    constraint seen_sources_references_external_source
+      foreign key (external_source_name, derivation_group)
+      references merlin.external_source (key, derivation_group_name) match simple
       on delete cascade
 );