Adopt SummerCMS v0.1.1 admin features

Datepickers on native time.Time / lagoon.Date fields, file uploads on
materials, readings and class sessions managed from the course form
(course_id made nullable).

controllers/hooks.go

@@ -14,9 +14,10 @@ const (
 	PermMaterials = "jz.bm.access_materials"
 )
 
-// temporalHooks checks a model's Date and DateTime columns before every admin
-// save and answers a bad value as a 422 on its field. lagoon.Validate has no
-// date rules, so the model checks them itself (models.TemporalValidator).
+// temporalHooks checks the order of a model's dates before every admin save
+// and answers a bad value as a 422 on its field. lagoon.Validate cannot
+// compare two fields, so the model checks them itself
+// (models.TemporalValidator).
 type temporalHooks struct{}
 
 func (temporalHooks) FormBeforeCreate(_ context.Context, model any) error {