Revise permissions for work item relations
## Summary The Product Planning group will be working streamlining permissions for the the ability to create relationships (relates to, blocks, is blocked by) between records. Today, we require the Reporter role to complete this action, however, since Guest users can already access this information we've determined that this task should also be possible for Guests. ## Proposal | Relation | Description | {-Current Permissions-} | {+New Permissions+} | Issue | | ------ | ------ | ------ | ------ | ------ | | Epic-Epic (vertical) | Link epics as blocked/blocking/related | `Reporter` access in both epics | `Guest` access in both epics | https://gitlab.com/gitlab-org/gitlab/-/issues/381308 | | Epic-Epic (horizontal) | Add/remove child/parent epic | `Reporter` access in both epics | `Guest` access in both epics | https://gitlab.com/gitlab-org/gitlab/-/issues/382503 | | Epic-Issue (vertical) | Add/remove child issue | read access in epic (non-member if group is public, `Guest` if private) / `Reporter` access in issue | `Guest` access in issue and epic | https://gitlab.com/gitlab-org/gitlab/-/issues/382506 | | Issue-Issue (horizontal)|Link issues as blocked/blocking/related |`Reporter` access in both issues | `Guest` access in both issues | https://gitlab.com/gitlab-org/gitlab/-/issues/404798| | Issue-Task (vertical) | Add task to an issue | `Reporter` access in both work items | `Guest` access in both issue and task|https://gitlab.com/gitlab-org/gitlab/-/issues/404799 | | Objective-Objective (vertical) | Add a child objective to an objective | `Reporter` access in both work items |`Guest` access in both work items | https://gitlab.com/gitlab-org/gitlab/-/issues/404795 | | Objective-Key Result (vertical) | Add a key result to an objective | `Reporter` access in both work items | `Guest` access in both work items | https://gitlab.com/gitlab-org/gitlab/-/issues/404796 |
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