Create HIP-423 work plan

[tinker-michaelj]

Problem

As we want to introduce the modularized implementation of HIP-423, we need a work plan, with special emphasis given to,

• Simplified throttles.
• State (re)organization that is appropriate for the block stream.
• Maximum simplicity of authorization checks.

Solution

Review HIP-423, the mono-service implementation, the current ScheduleService, and devise a family of work items.

Alternatives

No response