See
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2050#note_31851242

See
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2050#note_31851343

See
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2050#note_31779236

 - Fix capitalization mistake `setpendingReferences`
 - Remove optimistic deletion
 - Remove unused namespace/project returned from BE on DOM that we used
   to compare against

```
{
  relatedIssues: [{ issue }, { issue}],
  pendingReferences: ['ref1', 'ref2']
}
```

Address feedback in call with Filipa, Jacob, Victor, Oswaldo

Also see https://gitlab.slack.com/archives/C5P2BELCR/p1496779523230689

See https://github.com/vuejs/vue/issues/5829

Also added some `.off` for listeners

https://gitlab.com/gitlab-org/gitlab-ee/issues/2001#note_31580383

 - Use `idKey` attribute in `IssueToken` to not clash with native DOM `id`
   attribute
 - Add `removeRelatedIssue` and `removePendingRelatedIssue`
 - Move some template string logic into a variable before concating to
   make it easier to understand
 - Move `checkIsProcessable` and `replaceInList` as methods of the Vue
   component (better focus logic in one place)