feat: remove product-config crate dependency

Vendors the Flask Python-config writer locally (flask_config_writer) and drops
the airflow-operator's direct product-config dependency. The rendered
webserver_config.py is unchanged (the vendored writer is byte-for-byte faithful
to the crate). product-config remains a transitive dependency via
stackable-operator.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: adwk67

Cargo.lock

@@ -10,7 +10,6 @@ edition = "2021"
 repository = "https://github.com/stackabletech/airflow-operator"
 
 [workspace.dependencies]
-product-config = { git = "https://github.com/stackabletech/product-config.git", tag = "0.8.0" }
 stackable-operator = { git = "https://github.com/stackabletech/operator-rs.git", features = [
   "crds",
   "webhook",

Cargo.nix

@@ -9,7 +9,6 @@ repository.workspace = true
 publish = false
 
 [dependencies]
-product-config.workspace = true
 stackable-operator.workspace = true
 
 anyhow.workspace = true

Cargo.toml

@@ -6,7 +6,6 @@ use std::{
 };
 
 use const_format::concatcp;
-use product_config::flask_app_config_writer::{self, FlaskAppConfigWriterError};
 use snafu::{OptionExt, ResultExt, Snafu};
 use stackable_operator::{
     builder::{
@@ -93,6 +92,7 @@ use crate::{
         v1alpha2,
     },
     env_vars::{self, build_airflow_template_envs},
+    flask_config_writer::{self, FlaskAppConfigWriterError},
     operations::{
         graceful_shutdown::{
             add_airflow_graceful_shutdown_config, add_executor_graceful_shutdown_config,
@@ -754,7 +754,7 @@ fn build_rolegroup_config_map(
 
     let temp_file_footer: Option<String> = config.remove(CONFIG_OVERRIDE_FILE_FOOTER_KEY);
 
-    flask_app_config_writer::write::<AirflowConfigOptions, _, _>(
+    flask_config_writer::write::<AirflowConfigOptions, _, _>(
         &mut config_file,
         config.iter(),
         PYTHON_IMPORTS,

rust/operator-binary/Cargo.toml

@@ -1,6 +1,5 @@
 use std::collections::{BTreeMap, BTreeSet, HashMap};
 
-use product_config::flask_app_config_writer::{FlaskAppConfigOptions, PythonType};
 use serde::{Deserialize, Serialize};
 use snafu::{OptionExt, ResultExt, Snafu};
 use stackable_operator::{
@@ -56,6 +55,7 @@ use crate::{
             CeleryBrokerConnection, CeleryResultBackendConnection, MetadataDatabaseConnection,
         },
     },
+    flask_config_writer::{FlaskAppConfigOptions, PythonType},
     util::role_service_name,
 };