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

• 594

• 615

• 620

• 599

• 601

• 602

• 603

• 605

• 628

• 630

• 631

  • Closes #619

• 637

  • Closes #632

• 640

  • Closes #639

• 641

  • Closes #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.

• 615

• 619

• 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!!!