chore: remove _old_uid hack (#11277)

The virtual session code creates an in-memory session, and only upon release does it copy it to the actual session store. This makes a lot of sense to avoid operations on session stores with potentially high cost for I/O.

This commit removes a weird hack used in this code: virtual sessions were always created with an _old_uid=0 key/value pair, which was taken into account when checking if the session needed to be persisted.

As I could not find _any_ use of _old_uid in the code base, this looks like something worth removing.

The first ever mention of _old_uid is b33f7f792b and even there it is part of a
newly added file with no additional information. So likely code copied over from another project?

- no tests to add, remove or change
- not relevant for documentation
- not relevant for release notes

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11277
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Nils Goroll <nils.goroll@uplex.de>
Co-committed-by: Nils Goroll <nils.goroll@uplex.de>

modules/session/virtual.go

@@ -64,7 +64,6 @@ func (o *VirtualSessionProvider) Read(sid string) (session.RawStore, error) {
 		return o.provider.Read(sid)
 	}
 	kv := make(map[any]any)
-	kv["_old_uid"] = "0"
 	return NewVirtualStore(o, sid, kv), nil
 }
 
@@ -159,7 +158,7 @@ func (s *VirtualStore) Release() error {
 	// Now need to lock the provider
 	s.p.lock.Lock()
 	defer s.p.lock.Unlock()
-	if oldUID, ok := s.data["_old_uid"]; (ok && (oldUID != "0" || len(s.data) > 1)) || (!ok && len(s.data) > 0) {
+	if len(s.data) > 0 {
 		// Now ensure that we don't exist!
 		realProvider := s.p.provider