User Story:

A specific goal and outcome for an end user. There should be only one, otherwise you want to split out the ticket.

Similar to watchlist expiries, it should be possible for a user to set the watchlist labels for a page after they've clicked the watchstar (or watch link, on skins without a star).
A new MultiselectLookup field will be added to the notification (or toast) that appears after watching a page.

Acceptance criteria:

• A new MultiselectLookup field is present on the notification, with which it is possible to autocomplete on any of a user's watchlist labels. The labels are available from the action=userinfo API, and should not be loaded at page load time.
• There will be a hyperlink from there to Special:WatchlistLabels.
• Any number of labels will be able to be selected. As each is selected (i.e. its InfoChip appears) the set of labels is saved. This avoids the need for a 'save' button, and follows the behaviour of the expiry dropdown.
• No new labels are able to be created from this place.
• The action=watch API is updated to accept label IDs for assigning.

Details for QA:

Example suggestions for test cases or instructions for approaching testing

Designs:

Links or screenshot of design