Add stories to an epic

Bulk-adds backlog items of type STORY to the epic identified by id, up to a maximum of 100 stories per epic. To see the current count, fetch the epic with include=EPIC_STORIES and check relationships.epicStories.meta.count.

Note that id in the path is the epic's id, while each id inside the request body's data array is a story's id.

A story that already belongs to a different epic is moved rather than duplicated, since a story can only belong to one epic at a time. Stories that are already on this epic are left as-is and are not duplicated.

This endpoint applies a best-effort, partial-success model for invalid items: any story in data that is not found, is not of type STORY (e.g. it's a bug or another epic - no nested epics), or belongs to a private team the caller cannot access, is reported in the errors array along with its id and the reason, without blocking the rest of the request. Stories already on this epic are left as-is and don't count as new additions.

Capacity is enforced as all-or-nothing: if adding every valid, not-yet-associated story in data would exceed the 100-story limit, none of them are added, and a single error in errors reports how many stories were requested versus how many could actually fit. (Invalid items such as bugs or non-existent ids don't count toward this limit either way.)