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/courses.go

@@ -3,6 +3,9 @@
 package controllers
 
 import (
+	"context"
+
+	"git.golem15.com/golem15/summercms/modules/cabana"
 	"git.golem15.com/golem15/summercms/modules/pact"
 	"git.golem15.com/jakub/sm-bm-plugin/models"
 )
@@ -11,6 +14,10 @@ var (
 	_ pact.AdminController   = coursesAdmin{}
 	_ pact.AdminRecordSource = coursesAdmin{}
 	_ pact.AdminPermissioned = coursesAdmin{}
+
+	_ cabana.AdminRelationContractProvider = coursesAdmin{}
+	_ pact.RelationBeforeCreate            = coursesAdmin{}
+	_ pact.RelationBeforeUpdate            = coursesAdmin{}
 )
 
 // coursesAdmin is the admin controller for courses (przedmioty).
@@ -28,11 +35,41 @@ func (coursesAdmin) RequiredPermissions() []string {
 	return []string{PermCourses}
 }
 
-// TODO: requires SummerCMS change. The course form should embed relation
-// managers for its readings and class sessions, but cabana relation managers
-// only link and unlink belongsToMany rows through a pivot; hasMany children
-// cannot be listed or edited from the parent form. Readings and class
-// sessions have their own screens, filtered by course.
+// AdminRelationContracts binds the course form's relation managers for its
+// readings and class sessions. course_id is nullable, so both work on a
+// course that is not saved yet.
+func (coursesAdmin) AdminRelationContracts() []cabana.RelationContract {
+	return []cabana.RelationContract{
+		{
+			Name:       "readings",
+			Kind:       cabana.RelationHasMany,
+			NewRelated: func() any { return &models.Reading{} },
+			ForeignKey: "course_id",
+			Columns: map[string]string{
+				"title": "title", "author": "author", "is_required": "is_required", "sort_order": "sort_order",
+			},
+		},
+		{
+			Name:       "sessions",
+			Kind:       cabana.RelationHasMany,
+			NewRelated: func() any { return &models.ClassSession{} },
+			ForeignKey: "course_id",
+			Columns: map[string]string{
+				"starts_at": "starts_at", "ends_at": "ends_at", "room": "room", "kind": "kind",
+			},
+		},
+	}
+}
+
+// RelationBeforeCreate and RelationBeforeUpdate check that a class session
+// ends after it starts, as the class sessions screen does.
+func (coursesAdmin) RelationBeforeCreate(_ context.Context, _ string, _, child any) error {
+	return checkTemporal(child)
+}
+
+func (coursesAdmin) RelationBeforeUpdate(_ context.Context, _ string, _, child any) error {
+	return checkTemporal(child)
+}
 
 // CoursesController returns the jz.bm.courses admin controller.
 func CoursesController() pact.AdminController { return coursesAdmin{} }