IAM: Create and delete user from the legacy store (#107694)

* Add Create for User + DualWriter setup

* Add delete User

* Fix delete + access check

* Add tests for delete user

* Add tests for create user

* Fixes

* Use sqlx session to fix database locked issues

* wip authz checks

* legacyAccessClient

* Update legacyAccessClient, add tests for create user

* Close rows before running other queries

* Use ExecWithReturningId

* Verify deletion in the tests

* Add Validate and Mutate

* Other changes

* Address feedback

* Update tests

---------

Co-authored-by: Gabriel Mabille <gabriel.mabille@grafana.com>

pkg/registry/apis/iam/legacy/create_org_user.sql

@@ -0,0 +1,5 @@
+INSERT INTO {{ .Ident .OrgUserTable }} 
+  (org_id, user_id, role, created, updated)
+VALUES 
+  ({{ .Arg .Command.OrgID }}, {{ .Arg .Command.UserID }}, {{ .Arg .Command.Role }}, 
+   {{ .Arg .Command.Created }}, {{ .Arg .Command.Updated }})