Update response to return is_precompiled_letter

app/service/rest.py

@@ -68,7 +68,7 @@ from app.errors import (
     InvalidRequest,
     register_errors
 )
-from app.models import Service, EmailBranding, LETTER_TYPE, PRECOMPILED_TEMPLATE_NAME
+from app.models import Service, EmailBranding
 from app.schema_validation import validate
 from app.service import statistics
 from app.service.service_senders_schema import (
@@ -537,11 +537,7 @@ def get_monthly_template_usage(service_id):
                     'month': i.month,
                     'year': i.year,
                     'count': i.count,
-                    'precompiled_letter': (
-                        i.template_type == LETTER_TYPE and
-                        i.hidden and
-                        i.name == PRECOMPILED_TEMPLATE_NAME
-                    )
+                    'is_precompiled_letter': i.is_precompiled_letter
                 }
             )