Story LSMR-13: Fixed models errors

SAS/LSMR/src/lsmr/lsmrapp/models/specification.py

@@ -174,23 +174,23 @@ class Project(UserDefinedCommon):
 
 class RunSet(UserDefinedCommon):
     generator_parameters_doc = JSONField()
-    generator_template = ForeignKey('GeneratorTemplate', on_delete=SET_NULL)
+    generator_template = ForeignKey('GeneratorTemplate', on_delete=SET_NULL, null=True)
     project = ForeignKey('Project', related_name="run_sets", on_delete=CASCADE)
 
 
 class RunBlueprint(UserDefinedCommon):
     requirements_doc = JSONField()
-    copies = ForeignKey('RunBlueprint', related_name="copied_from", on_delete=SET_NULL)
+    copies = ForeignKey('RunBlueprint', related_name="copied_from", on_delete=SET_NULL, null=True)
     copy_reason = CharField(max_length=30,
                             choices=
-                            [i for i in CopyReasonChoice])
+                            [(item.name, item.value) for item in CopyReasonChoice])
     generator_param = CharField(max_length=200)  # todo: check if the field size is good enough
     run_set = ForeignKey(RunSet, related_name='run_blueprints', on_delete=CASCADE)
-    generator_source = ForeignKey(RunSet, on_delete=SET_NULL)
+    generator_source = ForeignKey(RunSet, on_delete=SET_NULL, null=True)
 
 
 class Run(SystemDefinedCommon):
     requirements_doc = JSONField()
     do_cancel = BooleanField()
-    template = ForeignKey(RunTemplate, on_delete=SET_NULL)
-    blueprint = ForeignKey(RunBlueprint, related_name='related_runs')
+    template = ForeignKey(RunTemplate, on_delete=SET_NULL, null=True)
+    blueprint = ForeignKey(RunBlueprint, related_name='related_runs', on_delete=CASCADE)