[QA] Tasks for Acceptance tests

### [OCISDEV-1406](https://kiteworks.atlassian.net/browse/OCISDEV-1406)

## Acceptance tests
- [ ] [OCISDEV-1001](https://kiteworks.atlassian.net/browse/OCISDEV-1001) — Improper access control on `/graph/v1.0/groups/[groupID]?$expand` PR: #12573 (Hint: New scenario under
`tests/acceptance/features/apiGraph/`)
- [ ] [OCISDEV-868](https://kiteworks.atlassian.net/browse/OCISDEV-868) — LDAP group-member
resolution broken when `posixGroup` uses `uniqueMember`. PR: #12814 & https://github.com/owncloud/reva/pull/719 (Scenario with a posixGroup fixture)
- [ ] [OCISDEV-670](https://kiteworks.atlassian.net/browse/OCISDEV-670) — EK users cannot log in to
Multi-Instance-OCIS. PR: #12101 (Login-flow scenario.)
- [ ] [OCISDEV-492](https://kiteworks.atlassian.net/browse/OCISDEV-492) — Space image not uploaded if larger than 7MB. PR: #12701 (Scenario asserting a proper validation error instead of silent failure.)
- [ ] [OCISDEV-388](https://kiteworks.atlassian.net/browse/OCISDEV-388) — Renaming a resource to its
current name fails without a meaningful error message: PR: #12784 (Scenario asserting a clear error.)

Start with the acceptance-test patterns under tests/acceptance/features/apiGraph/ and the referenced PRs for context. Add scenarios covering the five listed behaviors, including the posixGroup fixture and login, upload-validation, and rename-error cases. Done means each checklist item has an acceptance scenario that verifies the described behavior.

Written by the indexing model from the issue text.