TMSS-241: fix nullable cycles in project model

SAS/TMSS/src/tmss/tmssapp/migrations/0001_initial.py

-# Generated by Django 3.0.6 on 2020-07-14 21:21
+# Generated by Django 3.0.6 on 2020-07-14 21:50
 
 from django.conf import settings
 import django.contrib.postgres.fields
@@ -1019,7 +1019,7 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='project',
             name='cycles',
-            field=models.ManyToManyField(help_text='Cycles to which this project belongs (NULLable).', related_name='projects', to='tmssapp.Cycle'),
+            field=models.ManyToManyField(blank=True, help_text='Cycles to which this project belongs (NULLable).', related_name='projects', to='tmssapp.Cycle'),
         ),
         migrations.AddField(
             model_name='project',

SAS/TMSS/src/tmss/tmssapp/models/specification.py

@@ -276,7 +276,7 @@ class Cycle(NamedCommonPK):
 
 
 class Project(NamedCommonPK):
-    cycles = ManyToManyField('Cycle', related_name='projects', help_text='Cycles to which this project belongs (NULLable).')
+    cycles = ManyToManyField('Cycle', blank=True, related_name='projects', help_text='Cycles to which this project belongs (NULLable).')
     priority_rank = FloatField(null=False, help_text='Priority of this project w.r.t. other projects. Projects can interrupt observations of lower-priority projects.') # todo: add if needed: validators=[MinValueValidator(0.0), MaxValueValidator(1.0)]
     trigger_priority = IntegerField(default=1000, help_text='Priority of this project w.r.t. triggers.') # todo: verify meaning and add to help_text: "Triggers with higher priority than this threshold can interrupt observations of projects."
     can_trigger = BooleanField(default=False, help_text='True if this project is allowed to supply observation requests on the fly, possibly interrupting currently running observations (responsive telescope).')

SAS/TMSS/test/tmss_test_data_rest.py

@@ -141,7 +141,8 @@ class TMSSRESTTestDataCreator():
                 "priority_rank": 1.0,
                 "trigger_priority": 1000,
                 "can_trigger": False,
-                "private_data": True}
+                "private_data": True,
+                "cycles": []}
 
     def ResourceUnit(self):
             return  {