Create an onboarding plan for getting agencies on org model

[h-m-f-t]

Sub-issue description

This document should detail how we'll onboard agencies. This could be as simple as "ensure we have the right contacts at the right agencies and give them access" or detail our approach in a 1:1 synchronous session.

Acceptance criteria

• Meet to discuss this task, take notes
• Revise notes into a plan that helps us prepare for a comms plan/schedule
• Read/discuss the plan in org model sync

Additional context

• We should also include any internal or manual follow-on steps that need to be taken; e.g., prevent a domain from being requested "in" an onboarded agency's name.
• Though we should focus on federal agencies, we should consider what, if anything, we'd do different for non-federal agencies.