Checked the following locations:
* Model.save(): If there are parents involved, take the safe way and use
transactions since this should be an all or nothing operation.
If the model has no parents:
* Signals are executed before and after the previous existing
transaction -- they were never been part of the transaction.
* if `force_insert` is set then only one query is executed -> atomic
by definition and no transaction needed.
* same applies to `force_update`.
* If a primary key is set and no `force_*` is set Django will try an
UPDATE and if that returns zero rows it tries an INSERT. The first
case is completly save (single query). In the second case a
transaction should not produce different results since the update
query is basically a no-op then (might miss something though).
* QuerySet.update(): no signals issued, single query -> no transaction
needed.
* Model/Collector.delete(): This one is fun due to the fact that is
does many things at once.
Most importantly though: It does send signals as part of the
transaction, so for maximum backwards compatibility we need to be
conservative.
To ensure maximum compatibility the transaction here is removed only
if the following holds true:
* A single instance is being deleted.
* There are no signal handlers attached to that instance.
* There are no deletions/updates to cascade.
* There are no parents which also need deletion.
django.utils.http.urlsafe_base64_encode() now returns a string, not a
bytestring. Since URLs are represented as strings,
urlsafe_base64_encode() should return a string. All uses immediately
decoded the bytestring to a string anyway.
As the inverse operation, urlsafe_base64_decode() accepts a string.
When using include() without namespaces of some urlpatterns that
have an include() with namespace, the converters of the parent
include() weren't being used to convert the arguments of reverse().
SessionBase.decode() is the inverse operation to SessionBase.encode().
As SessionBase.encode() always returns a string, SessionBase.decode()
should always be passed a string argument. Fixed the file backend, which
was the only backend still passing a bytestring.
The old implementation considered objects initialized with an equivalent
signature different if some arguments were provided positionally instead of
as keyword arguments.
Refs #11964, #26167.
