feat: added a page to list cohorts of a course

- added a page /courses/<course>/manage that lists the active cohorts
- only accessible to mentors and staff
- also added a "manage the course" button on course page for mentors/staff

Issue #271

school/www/cohorts/index.py

@@ -0,0 +1,30 @@
+import frappe
+from .utils import get_course, add_nav
+
+def get_context(context):
+    context.no_cache = 1
+    context.course = get_course()
+    if frappe.session.user == "Guest":
+        frappe.local.flags.redirect_location = "/login?redirect-to=" + frappe.request.path
+        raise frappe.Redirect()
+
+    if not context.course:
+        context.template = "www/404.html"
+        return
+
+    context.cohorts = get_cohorts(context.course)
+
+    add_nav(context, "All Courses", "/courses")
+    add_nav(context, context.course.title, "/courses/" + context.course.name)
+
+def get_cohorts(course):
+    if "System Manager" in frappe.get_roles():
+        return course.get_cohorts()
+
+    staff_roles = frappe.get_all("Cohort Staff", filters={"course": course.name}, fields=["cohort"])
+    mentor_roles = frappe.get_all("Cohort Mentor", filters={"course": course.name}, fields=["cohort"])
+    roles = staff_roles + mentor_roles
+    print(roles)
+    names = {role.cohort for role in roles}
+    print(names)
+    return [frappe.get_doc("Cohort", name) for name in names]