Fixes up models to swap out on db type

This is a bit of a hack but it's the only way to truly dynamically swap
between models. We use a custom array field in sqllite and use standard
array field in postgres.

This also removes some faulty migrations

ui/backend/server/trackingserver_base/models.py

@@ -1,5 +1,6 @@
 import json
 
+from django.conf import settings
 from django.contrib.postgres.fields import ArrayField as BaseArrayField
 from django.db import models
 
@@ -56,14 +57,6 @@ class Meta:
         abstract = True
 
 
-def _is_postgres():
-    from django.conf import settings
-
-    out = settings.DB == "django.db.backends.postgresql"
-    assert out
-    return out
-
-
 class ArrayField(models.Field):
     """
     A field that acts like an ArrayField when using PostgreSQL and as a serialized TextField when using SQLite.
@@ -79,39 +72,29 @@ def deconstruct(self):
         return name, path, (self.base_field,) + tuple(args), kwargs
 
     def db_type(self, connection):
-        if _is_postgres():
-            return self.array_field.db_type(connection)
-        else:
-            return "text"
+        return "text"
 
     def from_db_value(self, value, expression, connection):
-        if _is_postgres():
-            return value
         if value is None:
             return value
         return json.loads(value)
 
     def to_python(self, value):
-        if _is_postgres():
-            return self.array_field.to_python(value)
         if isinstance(value, list) or value is None:
             return value
         return json.loads(value)
 
-    def get_prep_value(self, value):
-        if _is_postgres():
-            return self.array_field.get_prep_value(value)
+    def get_db_prep_save(self, value, connection):
         return json.dumps(value)
 
-    def get_db_prep_save(self, value, connection):
-        if _is_postgres():
-            return self.array_field.get_db_prep_save(value, connection)
+    def get_prep_value(self, value):
         return json.dumps(value)
 
     def value_to_string(self, obj):
-        if _is_postgres():
-            return self.array_field.value_to_string(obj)
         value = self.value_from_object(obj)
         if isinstance(value, list):
             return json.dumps(value)
         return value
+
+
+ArrayField = ArrayField if settings.DB == "django.db.backends.sqlite3" else BaseArrayField