feat: a calendar to subscribe to, and the backlog's corners

- Each person can subscribe their dates in Google Calendar, Outlook or
  Apple Calendar: GET /api/calendar/{token}.ics (no session) brings
  their unfinished tickets with a due date (assigned or followed), the
  planned and running sprints and the planned releases of their
  projects, as all-day events linking to the web. The token is made,
  renewed or dropped under /me/calendar (and in GraphQL); in the web,
  from «Calendario» in «Mi trabajo».
- The backlog panel keeps the selected rows' background inside its
  rounded corners.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/api/tracker/presenters/src/lib/graphql/calendar.resolver.ts

@@ -0,0 +1,32 @@
+import { Mutation, Query, Resolver } from '@nestjs/graphql';
+import { User } from '@task-stream/api/identity/domain';
+import { CurrentUser } from '@task-stream/api/identity/presenters';
+import { CalendarService } from '@task-stream/api/tracker/application';
+import { CalendarFeedGql } from './types';
+
+/** The signed-in person's calendar subscription (iCalendar URL). */
+@Resolver(() => CalendarFeedGql)
+export class CalendarResolver {
+  constructor(private readonly calendar: CalendarService) {}
+
+  @Query(() => CalendarFeedGql, {
+    nullable: true,
+    description: 'My calendar URL, if I made one',
+  })
+  myCalendarFeed(@CurrentUser() me: User) {
+    return this.calendar.mine(me.id);
+  }
+
+  @Mutation(() => CalendarFeedGql, {
+    description: 'A new secret calendar URL; the previous one stops working',
+  })
+  createCalendarFeed(@CurrentUser() me: User) {
+    return this.calendar.create(me.id);
+  }
+
+  @Mutation(() => Boolean, { description: 'My calendar URL stops working' })
+  async revokeCalendarFeed(@CurrentUser() me: User) {
+    await this.calendar.revoke(me.id);
+    return true;
+  }
+}

libs/api/tracker/presenters/src/lib/graphql/types.ts

@@ -625,6 +625,16 @@ export class MyNotificationsGql {
   unread!: number;
 }
 
+@ObjectType('CalendarFeed')
+export class CalendarFeedGql {
+  @Field({
+    description:
+      'Secret of the calendar URL: GET /api/calendar/{token}.ics (iCalendar, no session)',
+  })
+  token!: string;
+  @Field() createdAt!: string;
+}
+
 @ObjectType('NotificationSettings')
 export class NotificationSettingsGql {
   @Field({ description: 'Copies by e-mail' }) email!: boolean;