Support creating Trips from the frontend

*sigh* ... spent way too much time encoding/decoding date types...

I need my database, server, client, and JSON need to agree on types.

TL;DR:
- Add CSS for elm/datepicker library
- Create Common.allErrors to display UI errors
- Prefer Data.Time.Calendar.Day instead of newtype Date wrapper around Text

client/src/User.elm

@@ -1,9 +1,12 @@
 module User exposing (render)
 
+import Common
+import Date
+import DatePicker
 import Html exposing (..)
 import Html.Attributes exposing (..)
 import Html.Events exposing (..)
-import Maybe.Extra
+import Maybe.Extra as ME
 import RemoteData
 import State
 import Tailwind
@@ -11,6 +14,100 @@ import UI
 import Utils
 
 
+createTrip : State.Model -> Html State.Msg
+createTrip model =
+    div []
+        [ UI.header 3 "Plan Upcoming Trip"
+        , UI.textField
+            { pholder = "Where are you going?"
+            , inputId = "destination"
+            , handleInput = State.UpdateTripDestination
+            , inputValue = model.tripDestination
+            }
+        , div [ [ "flex" ] |> Tailwind.use |> class ]
+            [ UI.datePicker
+                { mDate = model.tripStartDate
+                , prompt = "Set departure date"
+                , prefix = "Departure: "
+                , picker = model.startDatePicker
+                , onUpdate = State.UpdateTripStartDate
+                }
+            , UI.datePicker
+                { mDate = model.tripEndDate
+                , prompt = "Set return date"
+                , prefix = "Return: "
+                , picker = model.endDatePicker
+                , onUpdate = State.UpdateTripEndDate
+                }
+            ]
+        , UI.textField
+            { pholder = "Comments?"
+            , inputId = "comment"
+            , handleInput = State.UpdateTripComment
+            , inputValue = model.tripComment
+            }
+        , UI.baseButton
+            { enabled =
+                List.all
+                    identity
+                    [ String.length model.tripDestination > 0
+                    , String.length model.tripComment > 0
+                    , ME.isJust model.tripStartDate
+                    , ME.isJust model.tripEndDate
+                    ]
+            , extraClasses = [ "my-4" ]
+            , handleClick =
+                case ( model.tripStartDate, model.tripEndDate ) of
+                    ( Nothing, _ ) ->
+                        State.DoNothing
+
+                    ( _, Nothing ) ->
+                        State.DoNothing
+
+                    ( Just startDate, Just endDate ) ->
+                        State.AttemptCreateTrip startDate endDate
+            , label = "Schedule trip"
+            }
+        ]
+
+
+trips : State.Model -> Html msg
+trips model =
+    div []
+        [ UI.header 3 "Upcoming Trips"
+        , case model.trips of
+            RemoteData.NotAsked ->
+                UI.paragraph "Somehow we've reached the user home page without requesting your trips data. Please report this to our engineering team at bugs@tripplaner.tld"
+
+            RemoteData.Loading ->
+                UI.paragraph "Loading your trips..."
+
+            RemoteData.Failure e ->
+                UI.paragraph ("Error: " ++ Utils.explainHttpError e)
+
+            RemoteData.Success xs ->
+                ul []
+                    (xs
+                        |> List.map
+                            (\trip ->
+                                li
+                                    [ [ "py-2" ]
+                                        |> Tailwind.use
+                                        |> class
+                                    ]
+                                    [ text
+                                        (Date.toIsoString trip.startDate
+                                            ++ " - "
+                                            ++ Date.toIsoString trip.endDate
+                                            ++ " -> "
+                                            ++ trip.destination
+                                        )
+                                    ]
+                            )
+                    )
+        ]
+
+
 render : State.Model -> Html State.Msg
 render model =
     div
@@ -23,17 +120,11 @@ render model =
             )
         ]
         [ UI.header 2 ("Welcome, " ++ model.username ++ "!")
-        , UI.simpleButton
+        , createTrip model
+        , trips model
+        , UI.textButton
             { label = "Logout"
             , handleClick = State.AttemptLogout
             }
-        , case model.logoutError of
-            Nothing ->
-                text ""
-
-            Just e ->
-                UI.errorBanner
-                    { title = "Error logging out"
-                    , body = Utils.explainHttpError e
-                    }
+        , Common.allErrors model
         ]