Add description to common image properties

Add the 'description' attribute to common image properties to allow
users to record the purpose of the image in a human-readable format
in an interoperable way.

Co-authored-by: zhangbailin <zhangbailin@inspur.com>
Co-authored-by: Brian Rosmaita <rosmaita.fossdev@gmail.com>

Change-Id: Id0b148190cfa5fb9851ad2085a6b1ac1e0e7e352
Blueprint: add-description-field-to-image

doc/source/user/common-image-properties.rst

@@ -60,3 +60,9 @@ https://docs.openstack.org/python-glanceclient/latest/cli/property-keys.html
 --------------
 
 The operating system version as specified by the distributor.
+
+**description**
+---------------
+
+A brief human-readable string, suitable for display in a user interface,
+describing the image.

etc/schema-image.json

@@ -22,7 +22,11 @@
         "type": "string"
     },
     "os_version": {
-        "description": "Operating system version as specified by the distributor",
+        "description": "Operating system version as specified by the distributor.",
+        "type": "string"
+    },
+    "description": {
+        "description": "A human-readable string describing this image.",
         "type": "string"
     }
 }

releasenotes/notes/add-description-common-image-property-95ab1139d41579d2.yaml

@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    A new common image property, 'description', has been added.  This
+    allows you to specify a brief human-readable description, suitable
+    for display in a user interface, on images.  It has been possible
+    to do this previously using a custom image property; this change
+    simply standardizes the usage in order to promote interoperability.
+    This change has no effect on any property named 'description' on
+    existing images, and it is not a required image property.