rewrite bookmarks using conat instead of the https nextjs api

[williamstein]

If for no other reason, than when doing dev I see this disconcerting list of errors in my log:

 POST /api/v2/bookmarks/get 501 in 36ms            
 POST /api/v2/bookmarks/get 501 in 48ms            
 POST /api/v2/bookmarks/get 501 in 20ms            
 POST /api/v2/jupyter/kernels 200 in 113ms                                                            
 POST /api/v2/jupyter/kernels 200 in 113ms                                                            
 POST /api/v2/bookmarks/get 501 in 33ms            
 POST /api/v2/bookmarks/get 501 in 20ms            
 POST /api/v2/bookmarks/get 501 in 24ms            
 POST /api/v2/bookmarks/get 501 in 38ms                                                               
 POST /api/v2/bookmarks/get 501 in 33ms                                                               
 POST /api/v2/bookmarks/get 501 in 83ms            
 POST /api/v2/bookmarks/get 501 in 149ms           
 POST /api/v2/bookmarks/get 501 in 35ms            
 POST /api/v2/bookmarks/get 501 in 41ms                                                               
 POST /api/v2/bookmarks/get 501 in 75ms                                                               
 POST /api/v2/bookmarks/get 501 in 76ms                                                               
 POST /api/v2/bookmarks/get 501 in 58ms                                                               
 POST /api/v2/bookmarks/get 501 in 31ms                                                               
 POST /api/v2/bookmarks/get 501 in 34ms  

(bookmarks are basically the only api call that regularly fails...)

[williamstein]

I assigned myself, since this is a good opportunity for me to understand the bookmarks code better.