appdata: Improve appdata for AppStream 1.0

- Implement appstreamcli validation.
- Correct required and recommended tags.
- Resolve required length errors.
- Include missing `<developer><name>` tag.
- Add the deprecated `developer_name` tag.
- Standardize the translation link with the link in the appdata file.

README.md

@@ -12,4 +12,4 @@ effort.
 - Homepage: <https://wiki.gnome.org/Apps/Calendar>
 - Report issues: <https://gitlab.gnome.org/GNOME/gnome-calendar/issues/>
 - Donate: <https://www.gnome.org/donate/>
-- Translate: <https://wiki.gnome.org/TranslationProject>
+- Translate: <https://l10n.gnome.org/module/gnome-calendar/>

data/appdata/meson.build

@@ -11,3 +11,14 @@ appdata = i18n.merge_file(
   install: true,
   install_dir: calendar_datadir / 'metainfo'
 )
+
+# Validate Appdata
+appstreamcli = find_program('appstreamcli', required: false)
+if appstreamcli.found()
+  test(
+    'Validate appstream file',
+    appstreamcli,
+    args: ['validate', '--no-net', '--explain', appdata.full_path()],
+    depends: appdata,
+  )
+endif

data/appdata/org.gnome.Calendar.appdata.xml.in.in

@@ -57,6 +57,10 @@
   <url type="translate">https://l10n.gnome.org/module/gnome-calendar/</url>
   <url type="contribute">https://wiki.gnome.org/Contribute</url>
   <project_group>GNOME</project_group>
+  <developer_name>The GNOME Project</developer_name>
+  <developer id="gnome.org">
+    <name>The GNOME Project</name>
+  </developer>
 
   <releases>
     <release date="2023-10-23" version="45.1" type="stable" />
@@ -407,18 +411,14 @@
   <translation type="gettext">gnome-calendar</translation>
   <launchable type="desktop-id">@appid@.desktop</launchable>
 
-  <requires>
-    <control>pointing</control>
-    <control>keyboard</control>
-    <control>touch</control>
-    <display_length compare="ge">small</display_length>
-  </requires>
-
   <recommends>
-    <control>pointing</control>
     <control>keyboard</control>
-    <display_length compare="ge">medium</display_length>
+    <control>pointing</control>
+    <control>touch</control>
   </recommends>
+  <requires>
+    <display_length compare="ge">360</display_length>
+  </requires>
 
   <content_rating type="oars-1.1">
     <content_attribute id="violence-cartoon">none</content_attribute>