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/Messages/Data/ChannelType.elm

@@ -0,0 +1,46 @@
+{-
+   Copyright 2020 Eike K. & Contributors
+
+   SPDX-License-Identifier: AGPL-3.0-or-later
+-}
+
+
+module Messages.Data.ChannelType exposing (Texts, de, gb)
+
+import Data.ChannelType exposing (ChannelType)
+
+
+type alias Texts =
+    ChannelType -> String
+
+
+gb : Texts
+gb ct =
+    case ct of
+        Data.ChannelType.Matrix ->
+            "Matrix"
+
+        Data.ChannelType.Gotify ->
+            "Gotify"
+
+        Data.ChannelType.Mail ->
+            "E-Mail"
+
+        Data.ChannelType.Http ->
+            "HTTP request"
+
+
+de : Texts
+de ct =
+    case ct of
+        Data.ChannelType.Matrix ->
+            "Matrix"
+
+        Data.ChannelType.Gotify ->
+            "Gotify"
+
+        Data.ChannelType.Mail ->
+            "E-Mail"
+
+        Data.ChannelType.Http ->
+            "HTTP Request"

modules/webapp/src/main/elm/Messages/Data/EventType.elm

@@ -0,0 +1,78 @@
+{-
+   Copyright 2020 Eike K. & Contributors
+
+   SPDX-License-Identifier: AGPL-3.0-or-later
+-}
+
+
+module Messages.Data.EventType exposing
+    ( Texts
+    , de
+    , gb
+    )
+
+import Data.EventType exposing (EventType(..))
+
+
+type alias Texts =
+    { name : String
+    , info : String
+    }
+
+
+gb : EventType -> Texts
+gb et =
+    case et of
+        TagsChanged ->
+            { name = "Tags changed"
+            , info = "Whenever a tag on an item is added or removed"
+            }
+
+        SetFieldValue ->
+            { name = "Set field value"
+            , info = "Whenever a custom field is set to a value"
+            }
+
+        DeleteFieldValue ->
+            { name = "Delete field value"
+            , info = "Whenever a custom field is removed"
+            }
+
+        JobSubmitted ->
+            { name = "Job submitted"
+            , info = "Whenever a new job is submitted"
+            }
+
+        JobDone ->
+            { name = "Job done"
+            , info = "Whenever a new job finished"
+            }
+
+
+de : EventType -> Texts
+de et =
+    case et of
+        TagsChanged ->
+            { name = "Tags geändert"
+            , info = "Wenn ein tag hinzugefügt oder entfernt wird"
+            }
+
+        SetFieldValue ->
+            { name = "Benutzerfeldwert ändert"
+            , info = "Wenn für ein Benutzerfeld ein Wert gesetzt wird"
+            }
+
+        DeleteFieldValue ->
+            { name = "Benutzerfeldwert entfernt"
+            , info = "Wenn der Wert für ein Benuzterfeld entfernt wird"
+            }
+
+        JobSubmitted ->
+            { name = "Auftrag gestartet"
+            , info = "Wenn ein neuer Auftrag gestartet wird"
+            }
+
+        JobDone ->
+            { name = "Auftrag beendet"
+            , info = "Wenn ein Auftrag beendet wurde"
+            }