First version of new ui based on tailwind

This drops fomantic-ui as css toolkit and introduces tailwindcss. With
tailwind there are no predefined components, but it's very easy to
create those. So customizing the look&feel is much simpler, most of
the time no additional css is needed.

This requires a complete rewrite of the markup + styles. Luckily all
logic can be kept as is. The now old ui is not removed, it is still
available by using a request header `Docspell-Ui` with a value of `1`
for the old ui and `2` for the new ui.

Another addition is "dev mode", where docspell serves assets with a
no-cache header, to disable browser caching. This makes developing a
lot easier.

modules/webapp/src/main/elm/Api.elm

@@ -50,6 +50,7 @@ module Api exposing
     , getJobQueueState
     , getJobQueueStateIn
     , getMailSettings
+    , getNewUi
     , getNotifyDueItems
     , getOrgFull
     , getOrgLight
@@ -120,6 +121,7 @@ module Api exposing
     , startOnceScanMailbox
     , startReIndex
     , submitNotifyDueItems
+    , toggleNewUi
     , toggleTags
     , unconfirmMultiple
     , updateNotifyDueItems
@@ -1931,6 +1933,25 @@ getItemProposals flags item receive =
         }
 
 
+toggleNewUi : Flags -> (Result Http.Error BasicResult -> msg) -> Cmd msg
+toggleNewUi flags receive =
+    Http2.authPost
+        { url = flags.config.baseUrl ++ "/api/v1/sec/newui"
+        , account = getAccount flags
+        , body = Http.emptyBody
+        , expect = Http.expectJson receive Api.Model.BasicResult.decoder
+        }
+
+
+getNewUi : Flags -> (Result Http.Error BasicResult -> msg) -> Cmd msg
+getNewUi flags receive =
+    Http2.authGet
+        { url = flags.config.baseUrl ++ "/api/v1/sec/newui"
+        , account = getAccount flags
+        , expect = Http.expectJson receive Api.Model.BasicResult.decoder
+        }
+
+
 
 --- Helper