tags: Add new _USER_RATING tag

Adds a new tag for user favorite media rating.
User rating informs how much (from 0 to 100) a user
'likes' a media.
Having an percent uint range for this is easy to map into other scales,
like some players that allow users to attribute 'stars' to its
media.

API: GST_TAG_USER_RATING

Fixes #520697

docs/gst/gstreamer-sections.txt

@@ -2190,6 +2190,7 @@ GST_TAG_SHOW_SEASON_NUMBER
 GST_TAG_LYRICS
 GST_TAG_COMPOSER_SORTNAME
 GST_TAG_GROUPING
+GST_TAG_USER_RATING
 
 gst_tag_register
 gst_tag_merge_use_first

gst/gsttaglist.c

@@ -323,6 +323,10 @@ _gst_tag_initialize (void)
       _("Groups related media that spans multiple tracks, like the different "
           "pieces of a concerto. It is a higher level than a track, "
           "but lower than an album"), NULL);
+  gst_tag_register (GST_TAG_USER_RATING, GST_TAG_FLAG_META, G_TYPE_UINT,
+      _("user rating"),
+      _("Rating attributed by a user. The higher the rank, "
+          "the more the user likes this media"), NULL);
 }
 
 /**

gst/gsttaglist.h

@@ -879,6 +879,16 @@ gboolean     gst_tag_list_get_buffer_index  (const GstTagList * list,
  * Since: 0.10.26
  */
 #define GST_TAG_GROUPING                          "grouping"
+/**
+ * GST_TAG_USER_RATING
+ *
+ * Rating attributed by a person (likely the application user).
+ * The higher the value, the more the user likes this media
+ * (unsigned int from 0 to 100)
+ *
+ * Since: 0.10.29
+ */
+#define GST_TAG_USER_RATING                       "user-rating"
 
 G_END_DECLS