Add assignment based on last usage.

deploy/crds/vmpools-crd.yaml

@@ -16,6 +16,15 @@ spec:
             spec:
               type: object
               properties:
+                retention:
+                  description: >-
+                    Defines the timeout for assignments. The time may be
+                    specified as ISO 8601 time or duration. When specifying
+                    a duration, it will be added to the last time the VM's 
+                    console was used to obtain the timeout.
+                  type: string
+                  pattern: '^(?:\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])T(?:[01]\d|2[0-3]):[0-5]\d:[0-5]\d(?:\.\d{1,9})?(?:Z|[+-](?:[01]\d|2[0-3])(?:|:?[0-5]\d))|P(?:\d+Y)?(?:\d+M)?(?:\d+W)?(?:\d+D)?(?:T(?:\d+[Hh])?(?:\d+[Mm])?(?:\d+(?:\.\d{1,9})?[Ss])?)?)$'
+                  default: "PT1h"
                 permissions:
                   type: array
                   description: >-