Restricted Magnum service state to 'up' and 'down'

Magnum service state could have any string having length 1-255.
This patch restricts value to be one of the following
  - up
  - down

Change-Id: I740e0379b78c08cbd9ded7ca7bd1bbdd92d44e90
Closes-bug: #1609216

magnum/api/controllers/v1/magnum_services.py

@@ -21,6 +21,7 @@ from magnum.api import expose
 from magnum.api import servicegroup as svcgrp_api
 from magnum.common import policy
 from magnum import objects
+from magnum.objects import fields
 
 
 class MagnumService(base.APIBase):
@@ -31,7 +32,7 @@ class MagnumService(base.APIBase):
     binary = wtypes.StringType(min_length=1, max_length=255)
     """Name of the binary"""
 
-    state = wtypes.StringType(min_length=1, max_length=255)
+    state = wtypes.Enum(str, *fields.MagnumServiceState.ALL)
     """State of the binary"""
 
     id = wsme.wsattr(wtypes.IntegerType(minimum=1))

magnum/objects/fields.py

@@ -79,6 +79,18 @@ class DockerStorageDriver(fields.Enum):
             valid_values=DockerStorageDriver.ALL)
 
 
+class MagnumServiceState(fields.Enum):
+    ALL = (
+        up, down
+    ) = (
+        'up', 'down',
+    )
+
+    def __init__(self):
+        super(MagnumServiceState, self).__init__(
+            valid_values=MagnumServiceState.ALL)
+
+
 class ListOfDictsField(fields.AutoTypedField):
     AUTO_TYPE = fields.List(fields.Dict(fields.FieldType()))
 
@@ -87,6 +99,10 @@ class BayStatusField(fields.BaseEnumField):
     AUTO_TYPE = BayStatus()
 
 
+class MagnumServiceField(fields.BaseEnumField):
+    AUTO_TYPE = MagnumServiceState()
+
+
 class ContainerStatusField(fields.BaseEnumField):
     AUTO_TYPE = ContainerStatus()