Items: Add unit metadata for UoM (Number:) Items (#1901)

Fixes #1890.

This adds the `unit` metadata from
openhab/openhab-core#3481 to the pre-defined
metadata namespaces for UoM Items (Item type `Number:`) and provides a
metadata edit page for it.

Once openhab/openhab-core#3611 is merged, the
Item create page will be adjusted to set the `unit` metadata to the
system default on Item creation.

--
Signed-off-by: Florian Hotze <florianh_dev@icloud.com>

bundles/org.openhab.ui/web/src/assets/definitions/metadata/namespaces.js

@@ -1,4 +1,5 @@
 export default [
+  { name: 'unit', label: 'Unit' },
   { name: 'stateDescription', label: 'State Description' },
   { name: 'commandDescription', label: 'Command Options' },
   { name: 'synonyms', label: 'Synonyms' },

bundles/org.openhab.ui/web/src/components/item/metadata/item-metadata-menu.vue

@@ -4,15 +4,15 @@
       <f7-list>
         <ul>
           <f7-list-item
-            v-for="namespace in wellKnownNamespaces" :key="namespace"
+            v-for="namespace in wellKnownNamespaces" :key="namespace.name"
             :link="'/settings/items/' + item.name + '/metadata/' + namespace.name"
             :title="namespace.label"
             :after="namespace.value || 'Not Set'" />
         </ul>
         <ul v-if="customNamespaces.length > 0">
           <f7-list-item divider />
           <f7-list-item
-            v-for="namespace in customNamespaces" :key="namespace"
+            v-for="namespace in customNamespaces" :key="namespace.name"
             :link="'/settings/items/' + item.name + '/metadata/' + namespace.name"
             :title="namespace.label"
             :after="namespace.value || 'Not Set'" />
@@ -37,6 +37,9 @@ export default {
       metadataNamespaces: MetadataNamespaces
     }
   },
+  beforeMount () {
+    if (this.item.type.indexOf('Number:') < 0) this.metadataNamespaces = this.metadataNamespaces.filter(n => n.name !== 'unit')
+  },
   computed: {
     editableNamespaces () {
       if (!this.item.metadata) return []
@@ -54,9 +57,9 @@ export default {
     },
     wellKnownNamespaces () {
       return this.editableNamespaces
-        .filter((n) => MetadataNamespaces.some((wk) => wk.name === n.name))
+        .filter((n) => this.metadataNamespaces.some((wk) => wk.name === n.name))
         .map((n) => {
-          const wellKnown = MetadataNamespaces.find((wk) => wk.name === n.name)
+          const wellKnown = this.metadataNamespaces.find((wk) => wk.name === n.name)
           return {
             ...n,
             label: wellKnown.label
@@ -65,7 +68,7 @@ export default {
     },
     customNamespaces () {
       return this.editableNamespaces
-        .filter((n) => !MetadataNamespaces.some((wk) => wk.name === n.name))
+        .filter((n) => !this.metadataNamespaces.some((wk) => wk.name === n.name))
         .map((n) => {
           return {
             ...n,
@@ -87,7 +90,7 @@ export default {
         buttons: [
           [
             { label: true, text: 'Well-known namespaces' },
-            ...MetadataNamespaces.map((n) => {
+            ...this.metadataNamespaces.map((n) => {
               return {
                 text: n.label,
                 color: 'blue',

bundles/org.openhab.ui/web/src/components/item/metadata/item-metadata-unit.vue

@@ -0,0 +1,32 @@
+<template>
+  <div>
+    <f7-block-header>
+      <b style="color: var(--f7-theme-color) !important;">WARNING: Changing the internal unit can corrupt your persisted data!</b>
+    </f7-block-header>
+    <f7-list>
+      <f7-list-input
+        label="Unit"
+        name="value"
+        ref="value"
+        type="text"
+        placeholder="leave empty to use system default"
+        :value="metadata.value"
+        @blur="(evt) => metadata.value = evt.target.value" />
+    </f7-list>
+    <f7-block-footer class="param-description">
+      <small>All processed values are internally normalized to the specified <code>unit</code>. The normalized value is used to propagate the value to external integrations (e.g. persistence, REST API, WebSocket) so these values will always have the specified unit and scale.
+        <br>
+        Changing the <code>unit</code> will change the values that these systems receive.
+        <br>
+        <br>
+        Additionally the <code>unit</code> will be used in UIs if no unit is specified for the state description. The state description is used for display purpose only, it can contain any compatible unit and will not affect the internal <code>unit</code>.
+      </small>
+    </f7-block-footer>
+  </div>
+</template>
+
+<script>
+export default {
+  props: ['itemName', 'metadata', 'namespace']
+}
+</script>

bundles/org.openhab.ui/web/src/pages/settings/items/metadata/item-metadata-edit.vue

@@ -66,6 +66,7 @@ import YAML from 'yaml'
 import MetadataNamespaces from '@/assets/definitions/metadata/namespaces.js'
 
 import ItemMetadataItemDescription from '@/components/item/metadata/item-metadata-itemdescription.vue'
+import ItemMetadataUnit from '@/components/item/metadata/item-metadata-unit.vue'
 import ItemMetadataSynonyms from '@/components/item/metadata/item-metadata-synonyms.vue'
 import ItemMetadataWidget from '@/components/item/metadata/item-metadata-widget.vue'
 import ItemMetadataWidgetOrder from '@/components/item/metadata/item-metadata-widgetorder.vue'
@@ -109,6 +110,8 @@ export default {
         case 'stateDescription':
         case 'commandDescription':
           return ItemMetadataItemDescription
+        case 'unit':
+          return ItemMetadataUnit
         case 'synonyms':
           return ItemMetadataSynonyms
         case 'widget':