Update schedule and operation Schemas

- Add a validation step to ensure the schedule field has a valid cron
  syntax.
- Change the obfuscator field to be required.

app/objects/c_operation.py

@@ -47,7 +47,7 @@ class Meta:
     planner = ma.fields.Nested(PlannerSchema())
     start = ma.fields.DateTime(format=BaseObject.TIME_FORMAT, dump_only=True)
     state = ma.fields.String()
-    obfuscator = ma.fields.String()
+    obfuscator = ma.fields.String(required=True)
     autonomous = ma.fields.Integer()
     chain = ma.fields.Function(lambda obj: [lnk.display for lnk in obj.chain])
     auto_close = ma.fields.Boolean()

app/objects/c_schedule.py

@@ -1,6 +1,7 @@
 import uuid
 
 import marshmallow as ma
+from croniter import croniter
 
 from app.objects.interfaces.i_object import FirstClassObjectInterface
 from app.objects.c_operation import OperationSchema
@@ -13,9 +14,14 @@ class Meta:
         unknown = ma.EXCLUDE
 
     id = ma.fields.String()
-    schedule = ma.fields.Time(required=True)
+    schedule = ma.fields.String(required=True, metadata={"example": "5 4 * * *"})
     task = ma.fields.Nested(OperationSchema())
 
+    @ma.validates('schedule')
+    def validate_schedule(self, value):
+        if not croniter.is_valid(value):
+            raise ma.ValidationError("Invalid cron syntax for schedule field.")
+
     @ma.post_load
     def build_schedule(self, data, **kwargs):
         return None if kwargs.get('partial') is True else Schedule(**data)