python/layout, general/architecture: Add lessons learned from Credere

docs/general/architecture.rst

@@ -20,3 +20,10 @@ When using :doc:`../python/django`, the workers are written as Django `managemen
 In other words, **nothing is a microservice**, where a `microservice <https://en.wikipedia.org/wiki/Microservices>`__ means a sub-service that is developed and deployed *independently* of others, as part of a service.
 
 Instead, we achieve loose coupling and proper encapsulation by other means: dividing program logic by UI responsibility (e.g. :ref:`model-template-view`); organizing a set of features into an `application <https://docs.djangoproject.com/en/4.2/ref/applications/#projects-and-applications>`__, when using Django; and otherwise organizing code carefully.
+
+.. _fat-models:
+
+Fat models
+----------
+
+If a function performs `CRUD operations <https://en.wikipedia.org/wiki/Create,_read,_update_and_delete>`__ and accepts only a database session and instance values as arguments, add this function as a method on the model's class.

docs/python/layout.rst

@@ -78,6 +78,22 @@ Static files
 
 -  Don't mix static files with Python files in the same directory.
 
+Module files
+------------
+
+-  Use a single module for all models.
+-  If a module defines names that are imported by only one other module, merge the modules unless:
+
+   - The module is a convention of a framework (for example, the files created by the `startapp <https://docs.djangoproject.com/en/4.2/intro/tutorial01/#creating-the-polls-app>`__ command in Django).
+   - There is a divide in terms of responsibility (for example, model and view).
+
+-  Don't split a module only to reduce its length.
+
+.. seealso::
+
+   -  :ref:`fat-models`
+   -  `FastAPI documentation <https://sqlmodel.tiangolo.com/tutorial/code-structure/#single-module-for-models>`__
+
 Filename conventions
 --------------------