Add human-readable age to snapshots

This is parsed server-side for consistent timing and to simplify the API
consumers.

daemon-common/common.py

@@ -441,6 +441,7 @@ def getDomainSnapshots(zkhandler, dom_uuid):
 
     all_snapshots = zkhandler.children(("domain.snapshots", dom_uuid))
 
+    current_timestamp = time.time()
     current_dom_xml = zkhandler.read(("domain.xml", dom_uuid))
 
     snapshots = list()
@@ -479,10 +480,36 @@ def getDomainSnapshots(zkhandler, dom_uuid):
             )
         )
 
+        _snap_timestamp = float(snap_timestamp)
+        snap_age_secs = int(current_timestamp) - int(_snap_timestamp)
+        snap_age = f"{snap_age_secs} seconds"
+        snap_age_minutes = int(snap_age_secs / 60)
+        if snap_age_minutes > 0:
+            if snap_age_minutes > 1:
+                s = "s"
+            else:
+                s = ""
+            snap_age = f"{snap_age_minutes} minute{s}"
+        snap_age_hours = int(snap_age_secs / 3600)
+        if snap_age_hours > 0:
+            if snap_age_hours > 1:
+                s = "s"
+            else:
+                s = ""
+            snap_age = f"{snap_age_hours} hour{s}"
+        snap_age_days = int(snap_age_secs / 86400)
+        if snap_age_days > 0:
+            if snap_age_days > 1:
+                s = "s"
+            else:
+                s = ""
+            snap_age = f"{snap_age_days} day{s}"
+
         snapshots.append(
             {
                 "name": snap_name,
                 "timestamp": snap_timestamp,
+                "age": snap_age,
                 "xml_diff_lines": snap_dom_xml_diff,
                 "rbd_snapshots": snap_rbd_snapshots,
             }