Release planning for 16.0.0

[consideRatio]

JupyterHub 4 is now released and I look to get z2jh 3 and tljh 1 bundle with various new dependencies with recent breaking changes. Let's try get a release out with oauthenticator!

Next version number: 16.0.0

We decided to go for 16.0.0 for the major refactoring.

Things I track to resolve before release

• [All] Authorize allowed_users, admin_users, _or_ other allowed/admin groups #594
• [CILogon] Require specification of allowed_idps? #615
• [All] Stop allowing all authenticated users by default #620
• Fix Content-Type header, should be x-www-form-urlencoded for token request, and not passed for other GET requests #599
• Fix bug in implementation of not yet released basic_auth config #601
• maint: cleanup already removed awscogito, azureadb2c, yandex #602
• maint: import Callable traitlet from jupyterhub #603
• Cannot override username_claim for helm chart anymore when using master #605
• refactor: separate deprecated config for readability #628
• maint: cleanup 0.7 workaround and adjust two non-exposed func names #630
• [All] breaking: add allow_existing_users config defaulting to False #631
  • Closes [All] Don't allow existing users when allowed_users is configured #619
• docs: coalesce v16 upgrade page into changelog, improve helpstrings #637
  • Closes Narrowing scope of docs for breaking changes, currently in reference/changelog and how-to/migrations #632
• [OpenShift] Remove ca_certs, deprecate validate_cert, fix unreleased regression #640
  • Closes [OpenShift] Fix no longer respected ca_certs config #639
• Add changelog for 16.0.0 #641
• Closes WIP: changelog for next release #612

[manics]

I think the big refactoring justifies a major release even if it's not required.

[consideRatio]

Wieee #594 is in! I'd like to go for the following PRs and then make a release. With #594, I think these changes are far easier to make and I expect them to be quite simple PRs.

• [CILogon] Require specification of allowed_idps? #615
• [All] Don't allow existing users when allowed_users is configured #619
• [All] Stop allowing all authenticated users by default #620

@GeorgianaElena do you think its the right call to go for #615?

[consideRatio]

Wieeeeeeeeeeeeeeeeeeeeee!!!! Thank you @GeorgianaElena @minrk and @manics for the push to get this all the way!!!