Allow markdown in survey question descriptions

closes indico#3366

indico/modules/events/surveys/models/items.py

@@ -21,6 +21,7 @@
 
 from indico.core.db import db
 from indico.core.db.sqlalchemy import PyIntEnum
+from indico.core.db.sqlalchemy.descriptions import DescriptionMixin, RenderMode
 from indico.modules.events.surveys.fields import get_field_types
 from indico.util.string import return_ascii, text_to_repr
 from indico.util.struct.enum import IndicoEnum
@@ -44,7 +45,7 @@ class SurveyItemType(int, IndicoEnum):
     text = 3
 
 
-class SurveyItem(db.Model):
+class SurveyItem(db.Model, DescriptionMixin):
     __tablename__ = 'items'
     __table_args__ = (db.CheckConstraint("type != {type} OR ("
                                          "title IS NOT NULL AND "
@@ -75,6 +76,9 @@ class SurveyItem(db.Model):
         'polymorphic_identity': None
     }
 
+    possible_render_modes = {RenderMode.markdown}
+    default_render_mode = RenderMode.markdown
+
     #: The ID of the item
     id = db.Column(
         db.Integer,
@@ -111,12 +115,6 @@ class SurveyItem(db.Model):
         nullable=True,
         default=_get_item_default_title
     )
-    #: The description of the item
-    description = db.Column(
-        db.Text,
-        nullable=False,
-        default=''
-    )
     #: If a section should be rendered as a section
     display_as_section = db.Column(
         db.Boolean,