(core) allow non-owners to remove themselves from sites/workspaces/docs

Summary:
For users who cannot otherwise change access to a resource, let
them remove themselves. Implemented via the standard endpoints
as a special exception that will process a request from a user
that would otherwise be denied, if the only contents of that
request are a removal of themselves.

Users who can change access are still not permitted to change their
own permissions or to remove themselves, as a precaution against
orphaning resources.

Test Plan: extended and updated tests

Reviewers: cyprien

Reviewed By: cyprien

Subscribers: dsagal

Differential Revision: https://phab.getgrist.com/D3367

app/client/ui/DocMenu.ts

@@ -432,6 +432,7 @@ export function makeDocOptionsMenu(home: HomeModel, doc: Document, renaming: Obs
       activeEmail: user ? user.email : null,
       resourceType: 'document',
       resourceId: doc.id,
+      resource: doc,
       linkToCopy: urlState().makeUrl(docUrl(doc)),
       reload: () => api.getDocAccess(doc.id),
       appModel: home.app,
@@ -463,10 +464,9 @@ export function makeDocOptionsMenu(home: HomeModel, doc: Document, renaming: Obs
       dom.cls('disabled', !roles.canEdit(orgAccess)),
       testId('pin-doc')
     ),
-    menuItem(manageUsers, "Manage Users",
-      dom.cls('disabled', !roles.canEditAccess(doc.access)),
+    menuItem(manageUsers, roles.canEditAccess(doc.access) ? "Manage Users" : "Access Details",
       testId('doc-access')
-    ),
+    )
   ];
 }