Add support for more generic notification

This is a start to have different kinds of notifications. It is
possible to be notified via e-mail, matrix or gotify. It also extends
the current "periodic query" for due items by allowing notification
over different channels. A "generic periodic query" variant is added
as well.

modules/webapp/src/main/elm/Comp/NotificationGotifyForm.elm

@@ -0,0 +1,117 @@
+{-
+   Copyright 2020 Eike K. & Contributors
+
+   SPDX-License-Identifier: AGPL-3.0-or-later
+-}
+
+
+module Comp.NotificationGotifyForm exposing (Model, Msg, init, initWith, update, view)
+
+import Api.Model.NotificationGotify exposing (NotificationGotify)
+import Comp.Basic as B
+import Data.NotificationChannel
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Html.Events exposing (onInput)
+import Messages.Comp.NotificationGotifyForm exposing (Texts)
+import Styles as S
+
+
+type alias Model =
+    { hook : NotificationGotify
+    }
+
+
+init : Model
+init =
+    { hook = Data.NotificationChannel.setTypeGotify Api.Model.NotificationGotify.empty
+    }
+
+
+initWith : NotificationGotify -> Model
+initWith hook =
+    { hook = Data.NotificationChannel.setTypeGotify hook
+    }
+
+
+type Msg
+    = SetUrl String
+    | SetAppKey String
+
+
+
+--- Update
+
+
+update : Msg -> Model -> ( Model, Maybe NotificationGotify )
+update msg model =
+    let
+        newHook =
+            updateHook msg model.hook
+    in
+    ( { model | hook = newHook }, check newHook )
+
+
+check : NotificationGotify -> Maybe NotificationGotify
+check hook =
+    Just hook
+
+
+updateHook : Msg -> NotificationGotify -> NotificationGotify
+updateHook msg hook =
+    case msg of
+        SetUrl s ->
+            { hook | url = s }
+
+        SetAppKey s ->
+            { hook | appKey = s }
+
+
+
+--- View
+
+
+view : Texts -> Model -> Html Msg
+view texts model =
+    div []
+        [ div
+            [ class "mb-2"
+            ]
+            [ label
+                [ for "gotifyurl"
+                , class S.inputLabel
+                ]
+                [ text texts.gotifyUrl
+                , B.inputRequired
+                ]
+            , input
+                [ type_ "text"
+                , onInput SetUrl
+                , placeholder texts.gotifyUrl
+                , value model.hook.url
+                , name "gotifyurl"
+                , class S.textInput
+                ]
+                []
+            ]
+        , div
+            [ class "mb-2"
+            ]
+            [ label
+                [ for "appkey"
+                , class S.inputLabel
+                ]
+                [ text texts.appKey
+                , B.inputRequired
+                ]
+            , input
+                [ type_ "text"
+                , onInput SetAppKey
+                , placeholder texts.appKey
+                , value model.hook.appKey
+                , name "appkey"
+                , class S.textInput
+                ]
+                []
+            ]
+        ]