Add input field to provide colors for tag categories

modules/webapp/src/main/elm/Data/Color.elm

@@ -0,0 +1,134 @@
+module Data.Color exposing
+    ( Color
+    , all
+    , allString
+    , fromString
+    , toString
+    )
+
+
+type Color
+    = Red
+    | Orange
+    | Yellow
+    | Olive
+    | Green
+    | Teal
+    | Blue
+    | Violet
+    | Purple
+    | Pink
+    | Brown
+    | Grey
+    | Black
+
+
+all : List Color
+all =
+    [ Red
+    , Orange
+    , Yellow
+    , Olive
+    , Green
+    , Teal
+    , Blue
+    , Violet
+    , Purple
+    , Pink
+    , Brown
+    , Grey
+    ]
+
+
+allString : List String
+allString =
+    List.map toString all
+
+
+fromString : String -> Maybe Color
+fromString str =
+    case String.toLower str of
+        "red" ->
+            Just Red
+
+        "orange" ->
+            Just Orange
+
+        "yellow" ->
+            Just Yellow
+
+        "olive" ->
+            Just Olive
+
+        "green" ->
+            Just Green
+
+        "teal" ->
+            Just Teal
+
+        "blue" ->
+            Just Blue
+
+        "violet" ->
+            Just Violet
+
+        "purple" ->
+            Just Purple
+
+        "pink" ->
+            Just Pink
+
+        "brown" ->
+            Just Brown
+
+        "grey" ->
+            Just Grey
+
+        "black" ->
+            Just Black
+
+        _ ->
+            Nothing
+
+
+toString : Color -> String
+toString color =
+    case color of
+        Red ->
+            "red"
+
+        Orange ->
+            "orange"
+
+        Yellow ->
+            "yellow"
+
+        Olive ->
+            "olive"
+
+        Green ->
+            "green"
+
+        Teal ->
+            "teal"
+
+        Blue ->
+            "blue"
+
+        Violet ->
+            "violet"
+
+        Purple ->
+            "purple"
+
+        Pink ->
+            "pink"
+
+        Brown ->
+            "brown"
+
+        Grey ->
+            "grey"
+
+        Black ->
+            "black"