On epics roadmap page we list all epics in the given time frame
without pagination (at least for the first iteration), in this
case it would be nice to use the existing issuables index logic
except pagination (see MR gitlab-ee!4281). For this reason this
patch allows to easily disable pagination.

Related gitlab-ee!4281

Fix Error 500 when repository has no avatar

Closes #42249

See merge request gitlab-org/gitlab-ce!16601

Resolve "Commits atom feed is double-escaped"

Closes #41208

See merge request gitlab-org/gitlab-ce!16603

Html code now works in commits atom feed `title` and `summary`.

Closes #42249

Use last_edited_at instead of updated_at for displaying issuable last change

Closes #41247

See merge request gitlab-org/gitlab-ce!16406

System hooks for Merge Requests

See merge request gitlab-org/gitlab-ce!14387

For issuable models we keep two timestamps:
updated_at which is updated whenever any model attribute is changed,
last_edited_at which is changed when only title or description is
changed.

In UI bellow description we display who and when updated the item. But
last_edited_by (used for 'who') is mistakenly combined with updated_at
(when), last_edited_at should be used instead.

Closes #41247