Fix machine request pickeling and settings (#6772)

* Fix machine request pickeling

* fix precommit

* fix: shared state between workers and main thread for machine registry

* remove last usage of legacy PUI form framework to fix machine edit/delete modal

* reset cache before initialization

* update documentation

* fix: invalidating cache

* implement machine registry hash to check if a reload is required

* trigger: ci

* fix: request bug

* fix: test

* trigger: ci

* add clear errors and improve restart hook

* auto initialize not initialized machines when changing active state

* fix: tests

docs/docs/extend/machines/overview.md

@@ -6,6 +6,9 @@ title: Machines
 
 InvenTree has a builtin machine registry. There are different machine types available where each type can have different drivers. Drivers and even custom machine types can be provided by plugins.
 
+!!! info "Requires Redis"
+    If the machines features is used in production setup using workers, a shared [redis cache](../../start/docker.md#redis-cache) is required to function properly.
+
 ### Registry
 
 The machine registry is the main component which gets initialized on server start and manages all configured machines.
@@ -21,6 +24,13 @@ The machine registry initialization process can be divided into three stages:
     2. The driver.init_driver function is called for each used driver
     3. The machine.initialize function is called for each machine, which calls the driver.init_machine function for each machine, then the machine.initialized state is set to true
 
+#### Production setup (with a worker)
+
+If a worker is connected, there exist multiple instances of the machine registry (one in each worker thread and one in the main thread) due to the nature of how python handles state in different processes. Therefore the machine instances and drivers are instantiated multiple times (The `__init__` method is called multiple times). But the init functions and update hooks (e.g. `init_machine`) are only called once from the main process.
+
+The registry, driver and machine state (e.g. machine status codes, errors, ...) is stored in the cache. Therefore a shared redis cache is needed. (The local in-memory cache which is used by default is not capable to cache across multiple processes)
+
+
 ### Machine types
 
 Each machine type can provide a different type of connection functionality between inventree and a physical machine. These machine types are already built into InvenTree.
@@ -86,6 +96,7 @@ The machine type class gets instantiated for each machine on server startup and
           - update
           - restart
           - handle_error
+          - clear_errors
           - get_setting
           - set_setting
           - check_setting