Context Navigation

Changes between Initial Version and Version 1 of Ticket #35349

initial	v1
13	13
14	14
15		The `atomic()`, `commit()` and other functions should ~~get~~ the write/transaction database under the hood.
	15	The `atomic()`, `commit()` and other functions should access the write/transaction database under the hood.
16	16	----
17	17	Note : I am developing an application that switches the database connection on per-tenant bases. The database configurations are added to settings.DATABASES at runtime in a middleware and then, using the `contextvars.ContextVar` thread-local variable, I am passing the database alias to use from a middleware to my custom database router. It works fine for reading and writing data outside the transactions, but it fails when it comes to transaction. I could potentially pass the value of `ContextVar` as an argument to all Transaction API calls, but it still fails for the third-party libraries that are mostly calling this functions without arguments. I have patched globally `django.db.transaction.DEFAULT_DB_ALIAS` to a stub string-like object that resolves dynamically in a runtime to a value of `ContextVar`, but that solution seems to be weird and I wish I could make it through configuring `DATABASE_ROUTERS`.