Address PR comments

- Changed the category relationship in Template from TemplateCategory to template_category
- dao_get_template_category_by_template_id now simply selects the template, and returns the associated template_category instead of using an expensive join

app/dao/template_categories_dao.py

@@ -4,7 +4,7 @@
 
 from app import db
 from app.dao.dao_utils import transactional
-from app.models import TemplateCategory
+from app.models import Template, TemplateCategory
 
 
 @transactional
@@ -18,13 +18,14 @@ def dao_update_template_category(template_category: TemplateCategory):
     db.session.add(template_category)
 
 
-def dao_get_template_category_by_id(template_category_id):
+def dao_get_template_category_by_id(template_category_id) -> TemplateCategory:
     return TemplateCategory.query.filter_by(id=template_category_id).one()
 
 
-def dao_get_template_category_by_template_id(template_id):
-    return TemplateCategory.query.join(TemplateCategory.templates).filter_by(id=template_id).one()
+def dao_get_template_category_by_template_id(template_id) -> TemplateCategory:
+    return Template.query.filter_by(id=template_id).one().template_category
 
 
-def dao_get_all_template_categories():
+# TODO: Add filters: Select all template categories used by at least 1 sms/email template
+def dao_get_all_template_categories(template_type=None, hidden=False):
     return TemplateCategory.query.order_by(asc(TemplateCategory.name_en)).all()

app/models.py

@@ -1213,7 +1213,7 @@ class Template(TemplateBase):
 
     service = db.relationship("Service", backref="templates")
     version = db.Column(db.Integer, default=0, nullable=False)
-    category = db.relationship("TemplateCategory", backref="templates")
+    category = db.relationship("template_category", backref="templates")
 
     folder = db.relationship(
         "TemplateFolder",
@@ -1235,6 +1235,9 @@ def get_link(self):
 
     @property
     def template_process_type(self):
+        """By default we use the process_type from TemplateCategory, but allow admins to override it on a per-template basis.
+           Only when overriden do we use the process_type from the template itself.
+        """
         if self.template_type == SMS_TYPE:
             return self.process_type if self.process_type else self.template_categories.sms_process_type
         elif self.template_type == EMAIL_TYPE: