Add the upgrade guide and the use case Consume a Workflow Update

UC-007, US-001.14 and US-001.15, the upgrade guide on the wiki in three
languages, and RC-044 to RC-046 with the traceability matrix.

Task: MIL-004#3

docs/uc-007/uc.md

@@ -0,0 +1,42 @@
+# UC-007: Consume a Workflow Update
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | UC-007 |
+| CrossReference | [UCD-001], [US-001], [SA-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-10 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | pending |
+
+---
+
+**Format:** Brief
+
+**Title:** Consume a Workflow Update
+**Scope:** Reusable Workflow Collection
+**Level:** user-goal
+**Primary Actor:** Software Engineer
+**Stakeholders:** S02, S05 (interests below)
+**Stories:** US-001.13, US-001.14, US-001.15
+
+## Brief
+
+When a new release of the shared workflows is announced, the Software Engineer reads its changelog entry to see whether it is breaking, changes the pinned version in one repository on a branch, opens a pull request and reads the run, and, when it is green, makes the same change in the other repositories.
+
+**Stakeholder interests**
+
+- S02 — an update is adopted deliberately, in one place first, and can be undone
+- S05 — consumers move to supported versions without a support request
+
+**Preconditions:** Releases are versioned with a changelog (the release process), and the repository calls the shared workflow at a version tag.
+
+**Postconditions (success guarantee):** The repository calls the new version, its pipeline still passes, and the previous version remains the way back.
+
+---
+
+[UCD-001]: ../use-case-diagram.md
+[US-001]: ../user-stories.md
+[SA-001]: ../stakeholder-analysis.md