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/PeriodicQueryTaskList.elm

@@ -0,0 +1,102 @@
+{-
+   Copyright 2020 Eike K. & Contributors
+
+   SPDX-License-Identifier: AGPL-3.0-or-later
+-}
+
+
+module Comp.PeriodicQueryTaskList exposing
+    ( Action(..)
+    , Model
+    , Msg
+    , init
+    , update
+    , view2
+    )
+
+import Comp.Basic as B
+import Data.ChannelType
+import Data.NotificationChannel
+import Data.PeriodicQuerySettings exposing (PeriodicQuerySettings)
+import Html exposing (..)
+import Html.Attributes exposing (..)
+import Messages.Comp.PeriodicQueryTaskList exposing (Texts)
+import Styles as S
+import Util.Html
+
+
+type alias Model =
+    {}
+
+
+type Msg
+    = EditSettings PeriodicQuerySettings
+
+
+type Action
+    = NoAction
+    | EditAction PeriodicQuerySettings
+
+
+init : Model
+init =
+    {}
+
+
+update : Msg -> Model -> ( Model, Action )
+update msg model =
+    case msg of
+        EditSettings settings ->
+            ( model, EditAction settings )
+
+
+
+--- View2
+
+
+view2 : Texts -> Model -> List PeriodicQuerySettings -> Html Msg
+view2 texts _ items =
+    div []
+        [ table [ class S.tableMain ]
+            [ thead []
+                [ tr []
+                    [ th [ class "" ] []
+                    , th [ class "text-center mr-2" ]
+                        [ i [ class "fa fa-check" ] []
+                        ]
+                    , th [ class "text-left " ] [ text texts.summary ]
+                    , th [ class "text-left hidden sm:table-cell mr-2" ]
+                        [ text texts.schedule ]
+                    , th [ class "text-left mr-2" ]
+                        [ text texts.connection ]
+                    ]
+                ]
+            , tbody []
+                (List.map (viewItem2 texts) items)
+            ]
+        ]
+
+
+viewItem2 : Texts -> PeriodicQuerySettings -> Html Msg
+viewItem2 texts item =
+    tr []
+        [ B.editLinkTableCell texts.basics.edit (EditSettings item)
+        , td [ class "w-px whitespace-nowrap px-2 text-center" ]
+            [ Util.Html.checkbox2 item.enabled
+            ]
+        , td [ class "text-left" ]
+            [ Maybe.withDefault "" item.summary
+                |> text
+            ]
+        , td [ class "text-left hidden sm:table-cell mr-2" ]
+            [ code [ class "font-mono text-sm" ]
+                [ text item.schedule
+                ]
+            ]
+        , td [ class "text-left py-4 md:py-2" ]
+            [ Data.NotificationChannel.channelType item.channel
+                |> Maybe.map Data.ChannelType.asString
+                |> Maybe.withDefault "-"
+                |> text
+            ]
+        ]