build and use local map of username to dbname

postgres/outputs.tf

@@ -3,6 +3,14 @@ output "postgres_instance_id" {
   value = stackit_postgresflex_instance.this.instance_id
 }
 
+locals {
+  # Build a map: username => db_name
+  user_to_db = {
+    for db in var.postgres_databases :
+    db.user_name => db.db_name
+  }
+}
+
 # Postgres Credential Output
 output "postgres_credentials" {
   value = {
@@ -12,7 +20,7 @@ output "postgres_credentials" {
       username = u.username
       password = u.password
       port     = u.port
-      db_name  = stackit_postgresflex_database.this[u.username].name
+      db_name  = stackit_postgresflex_database.this[local.user_to_db[u.username]].name
       uri      = u.uri
     }
   }