added delete support for assignments

Management.Web/Shared/Components/AssignmentForm/AssignmentForm.razor

@@ -1,6 +1,7 @@
 @using Management.Web.Shared.Components
 
 @inject CoursePlanner planner
+@inject CanvasService canvas
 
 @code {
 
@@ -106,6 +107,40 @@
     submissionTypes = newTypes;
     StateHasChanged();
   }
+
+  private async Task HandleDelete()
+  {
+    if(planner.LocalCourse != null)
+    {
+      var assignment = Assignment;
+      var currentModule = planner
+        .LocalCourse
+        .Modules
+        .First(m => 
+          m.Assignments
+            .Select(a => a.Id)
+            .Contains(Assignment.Id)
+        ) ?? throw new Exception("handling assignment delete, could not find module");
+      var newModules = planner.LocalCourse.Modules.Select(m => 
+        m.Name == currentModule.Name
+          ? m with 
+          {
+            Assignments = m.Assignments.Where(a => a.Id != assignment.Id).ToArray()
+          }
+          : m
+      ).ToArray();
+
+      planner.LocalCourse = planner.LocalCourse with 
+      {
+        Modules = newModules
+      };
+      if(assignment.CanvasId != null && planner.LocalCourse.CanvasId != null)
+      {
+        ulong courseId = planner.LocalCourse.CanvasId ?? throw new Exception("cannot delete if no course id");
+        await canvas.Assignments.Delete(courseId, assignment);
+      }
+    }
+  }
 }
 
 <Modal @ref="AssignmentModal" OnHide="@(() => OnHide())">
@@ -156,6 +191,11 @@
     </form>
   </Body>
   <Footer>
+    <ConfirmationModal 
+      Label="Delete" 
+      Class="btn btn-danger"
+      OnConfirmAsync="HandleDelete"
+    />
     <button class="btn btn-primary" @onclick="submitHandler">
       Save
     </button>