Initial access documentation for upgrades

[basvangijzel-DA]

Initial access documentation for zero downtime contract upgrades, based on initial topics here: 18993

[dylant-da]

@samuel-williams-da @hrischuk-da I think we can close this?

[samuel-williams-da]

I'd say after we merge the changes Curtis intends to make.

[dylant-da]

Update from last product grilling session: Curtis will

• Make inline changes that will need review
• Uncover some gaps that will need additional text to be closed
• Uncover missing topics that will need more additional tet

[dylant-da]

I've checked with Curtis, we can close