[BB-8162] Tackling sprints without enough tasks & last resort backlog

Ticket

PR to implement the changes resulting from the discussion at https://forum.opencraft.com/t/tackling-sprints-without-enough-tasks/1615

Introduces a new process for managing sprints with insufficient tasks, including a "Last resort" backlog and additional responsibilities for Sprint and Epic Planning Managers to ensure proper task estimation and workload balance.

1. Changes in processes/sprints.md:

   • A new section titled "Dealing with sprints without enough tasks" has been added. This section outlines a process to ensure that sprints are adequately filled with tasks. It includes:
     • A checklist for finding tasks if a sprint is underfilled.
     • Introduction of a “Last resort” backlog, a reserve of tasks to be used when all other options for filling a sprint are exhausted. This includes guidelines for using and populating this backlog.
     • A process for dealing with the use of the “Last resort” backlog, including the creation of a Root Cause Analysis (RCA) task.
     • Rendered: https://opencraft.gitlab.io/-/documentation/public/-/jobs/5764561052/artifacts/preview/processes/sprints.html#dealing-with-sprints-without-enough-tasks

2. Changes in roles/list.md:

   • Several updates were made to the role of the Sprint Planning Manager:
     • Ensuring all tasks have been estimated at the sprint estimation cut-off point.
     • Checking if the work scheduled matches the cell's capacity.
     • Addressing undercommitment in sprint preparation.
     • Overseeing backlog grooming to ensure it is properly maintained.
   • For Epic Planning Managers, new responsibilities include:
     • Managing the planned workload on epics to match cell capacity.
     • Actions to take if the workload is above or below cell capacity, such as informing the recruitment manager, creating tasks for epic owners, communicating with the business development specialist, and discussing the issue on the forum.
   • Rendered: https://opencraft.gitlab.io/-/documentation/public/-/jobs/5764561052/artifacts/preview/roles/list.html#sprint-planning-manager