[docs] updated documentation to include references to v3 services

[zenmonkeykstop]

Status

Ready for review

Description of Changes

Fixes #4632 .

Adds upgrade documentation for v3 onion services.
Updates installation and onboarding documentation to refer to v3 services
Updates development documentation to refer to v3 services.

Note: The documentation for the instance restore and workstation rebuild process has not been addressed in this PR, as it's unclear to me how they will work under v3. More investigation required. Notes have been added to those docs temporarily, to let admins know that they're not applicable to instances running v3 services.

Testing

Docs-only PR:

• review for clarity and correctness
• follow installation and instance test instructions to verify that they're correct.
• follow migration instructions to verify that servers are correctly updated to use v3
• follow admin and journalist workstation update instructions to verify that they are also cut over correctly to v3.

Checklist

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

[eloquence]

Thanks for taking this one on @zenmonkeykstop! Just a first round of comments based on visual review only.

[redshiftzero]

these docs look great, just a few comments inline

[rocodes]

LGTM. My only comment is that people who are not familiar with onion services (for example, a journalist trying to back up their Tails USB and encountering the term in the docs, or potentially an Admin taking over care of the instance from someone else) might not know what this means to them or if it matters. ("What's an onion service? How can I tell if mine is v2 or v3?"). The 'how can I tell' in v3_services is fairly clear, but the document definitely goes quickly into advanced territory.

This note aside, I'd say really clear and looking good.

[zenmonkeykstop]

@rocodes thanks, adding a bit more explanatory text re onion services.

[emkll]

Went through a visual review of these docs, they look great. I left a couple of small comments inline, though shouldn't block merge.

Has anyone performed a functional review of the instructions as part of their review? Else, I will perform a functional review first thing tomorrow, but it nothing stands out based on this visual review.

[kushaldas]

A few small changes requested.

[zenmonkeykstop]

Lemme know when it's good and I'll flatten this PR before merge.

[kushaldas]

Issues resolved. Approved.