Resolves https://github.com/unmojang/drasl/issues/39
* Use __Host- cookie prefix instead of setting Domain
See https://stackoverflow.com/a/64735551
* Unlinking OIDC accounts
* AllowPasswordLogin, OIDC docs, cleanup
* YggdrasilError
* Migrate existing password users without login
* API query/create/delete user OIDC identities
* test APICreateOIDCIdentity
* test APIDeleteeOIDCIdentity
* API Create users with OIDC identities
* OIDC: PKCE
* Use YggdrasilError in authlib-injector routes
* OIDC: AllowChoosingPlayerName
* recipes.md: Update for OIDC and deprecated config options
* OIDC: fix APICreateUser without password, validate oidcIdentities
* OIDC: error at complete-registration if no preferred player name
* Proper error pages
* MC_ prefix for Minecraft Tokens
Add a system for verifying that a user owns an account on another API
server (such as Mojang's). Drasl gives the user a skin to put on their
account, then checks that the account has the skin.
See `getChallenge` in `front.go`.
