Collection editing revamp

[emma-sg]

Closes #2328
Closes #2338

Tentatively ready for review...? This is a lot of changes, I'll split them out into sections below.

Changes

This is a fairly broad pass over the collection editing and sharing experience, focusing primarily on being able to edit collections from anywhere you might want to edit them (i.e. not just from within their detail page).

As part of these changes, we've removed the previous "metadata" editing dialog, and moved name, summary, thumbnail selection (detailed further below), and visibility into a new dialog that can be access from the org dashboard and the collections list, in addition to the collection detail pages.

Back-end changes

We've added a new thumbnailSource field to the Collection model, which preserves the page selected to be collection's thumbnail image. As such, we've separated thumbnail selection from initial replay view selection, though you can still use the initial replay view selection dialog to set the thumbnail if you wish. This field is set via three additional optional query parameters when uploading a thumbnail, and is returned to the client as part of the full collection object.

Front-end changes

This PR has changed quite a bit since the start of it & the call & issue that prompted it, I'd initially taken the route of trying to combine all collection editing interfaces into a single dialog, but along the way we figured out that doing so would require either stacked dialogs, which we decided against, or merging the "select archived items" dialog into the editing dialog, which would be a lot more unwieldy state logic to deal with, and potentially confusing options too coming from different places.

There's a few things left to do still:

• The current share dialog is still used, and still has visibility & thumbnail selection. This should be removed, and turned into just a dialog with url & embed information.
  Completed in 8eb179d
• The "edit collection" button should maybe be worded differently — or maybe removed entirely? The dialog it opens can be accessed from the inline edit button on the title/summary already, and from sharing settings
• We might not get to it this release, but it'd be great to have a button for setting the currently visible page in the replay to the initial replay view
  • I am de-scoping this. The current button works well enough for me to be happy releasing it. -HW
• Various issues when selecting thumbnails — we could exclude pages without thumbnails by excluding uploaded pages, it sounds like? Collection editing revamp #2332 (comment)
  Sort of handled 32078be with better error states & messaging, but could be improved on further
  • Checkmark on page selection input is a little misleading when selecting a page without a thumbnail — checkmark should change to a warning icon
  • Focus the URL field when users click the empty thumbnail in the presentation window
  • For some collections, selecting a page doesn't even show the "no preview" info in the preview — logic there isn't quite right
  • Sometimes selecting a page doesn't cause the thumbnail preview to update at all
• Rename "about" and "about this collection" to something having more to do specifically with the description
• Not doing this! -HW, ESG
• Rename "metadata" to something else (chose "details")
• Ensure language around "set initial view" is aligned.
• Add "Update starting URL" checkbox when updating thumbnail source
• Fix download button (api name changed and needed to be fixed on the front end)
  • Remove public download button from private collection view
• Update "Collection Settings" button to "Edit Collection Settings" icon button
• Add "Set Initial View" and "Edit Description" to action menu
• Remove share button visible when collection is private
• Have dashboard collection grid show all collections (maybe tab for public only?) — started on this in Allow showing all collections as well as just public ones in org dashboard #2379!
• Move globe icon on org dashboard back down to Public Collections section
• Rename "Public Gallery" -> "Public Collections Gallery" @SuaYoo

[ikreymer]

backend changes make sense! Should be good to go!