App with extension functions

src/cpl-application/cpl/application/abc/application_abc.py

@@ -1,10 +1,15 @@
 from abc import ABC, abstractmethod
+from typing import Callable, Self
 
 from cpl.application.host import Host
 from cpl.core.console.console import Console
 from cpl.dependency.service_provider_abc import ServiceProviderABC
 
 
+def __not_implemented__(package: str, func: Callable):
+    raise NotImplementedError(f"Package {package} is required to use {func.__name__} method")
+
+
 class ApplicationABC(ABC):
     r"""ABC for the Application class
 
@@ -17,6 +22,43 @@ class ApplicationABC(ABC):
     def __init__(self, services: ServiceProviderABC):
         self._services = services
 
+    @classmethod
+    def extend(cls, name: str | Callable, func: Callable[[Self], Self]):
+        r"""Extend the Application with a custom method
+
+        Parameters:
+            name: :class:`str`
+                Name of the method
+            func: :class:`Callable[[Self], Self]`
+                Function that takes the Application as a parameter and returns it
+        """
+        if callable(name):
+            name = name.__name__
+
+        setattr(cls, name, func)
+        return cls
+
+    def with_permissions(self, *args, **kwargs):
+        __not_implemented__("cpl-auth", self.with_permissions)
+
+    def with_migrations(self, *args, **kwargs):
+        __not_implemented__("cpl-database", self.with_migrations)
+
+    def with_seeders(self, *args, **kwargs):
+        __not_implemented__("cpl-database", self.with_seeders)
+
+    def with_extension(self, func: Callable[[Self, ...], None], *args, **kwargs):
+        r"""Extend the Application with a custom method
+
+        Parameters:
+            func: :class:`Callable[[Self], Self]`
+                Function that takes the Application as a parameter and returns it
+        """
+        assert func is not None, "func must not be None"
+        assert callable(func), "func must be callable"
+
+        func(self, *args, **kwargs)
+
     def run(self):
         r"""Entry point
 

src/cpl-application/cpl/application/application_builder.py

@@ -1,5 +1,5 @@
 import asyncio
-from typing import Type, Optional, Callable
+from typing import Type, Optional
 
 from cpl.application.abc.application_abc import ApplicationABC
 from cpl.application.abc.application_extension_abc import ApplicationExtensionABC
@@ -34,11 +34,11 @@ class ApplicationBuilder:
     def service_provider(self):
         return self._services.build()
 
-    def use_startup(self, startup: Type[StartupABC]) -> "ApplicationBuilder":
+    def with_startup(self, startup: Type[StartupABC]) -> "ApplicationBuilder":
         self._startup = startup
         return self
 
-    def use_extension(
+    def with_extension(
         self,
         extension: Type[ApplicationExtensionABC | StartupExtensionABC],
     ) -> "ApplicationBuilder":