Unnecessary issue edits by JIRA for already linked issue keys

Since a while we regularly see edits of PRs being made by JIRA. They seem to be triggered by the behavior to add links for issue keys in square brackets, however they also happen if the issue is already linked.

E.g. if the original PR description contains this:
```markdown
[ABC-123](https://company.atlassian.net/browse/ABC-123)
```

JIRA will edit it, so it becomes like this:
```markdown
[ABC-123](https://company.atlassian.net/browse/ABC-123)

[ABC-123]: https://company.atlassian.net/browse/ABC-123?atlOrigin=wifbejDagbaiQuoxyenefyixwikMuvdoatshEsp3drishkyuckerWofIcGeejyoabZyelCunnUmmUjojwa
```

Start by tracing the JIRA behavior that adds links for issue keys in square brackets, using the linked-issue example in this report as the reproduction case. Verify that an already linked [ABC-123] entry is left unchanged and that no extra reference definition is added; the issue provides no file or test names.

Written by the indexing model from the issue text.