Add user/project members enum input type

[marktaipan-cvisionai]

Category Feature Request

Problem If an annotator wants to log a user as part of an attribute field, they have to manually enter the name or username. This can get unwieldy in larger projects and is susceptible to data integrity issues. It is possible to create a static list with the existing enum option, but requires updating every time the membership list changes.

Request Add to the existing enum attribute type where project admins can set it to display a list of users currently associated with the project. It would also be preferable if the admin could set it to display FirstName LastName, or LastName, FirstName, or username. The actual field should be filled in with the user ID. The values/label field should be set to a blank dictionary.

[marktaipan-cvisionai]

Worth thinking about using the datalist HTML element since this combines both the autocomplete + dropdown searchability. In fact, it's probably worth seeing if this can just be styled so that it's the default enum-input behavior.