Missing PKCE is success in email verification flow

[scotttrinh]

Since end users might verify their email on a different device than the user agent they initiated the sign up (or sign in) flow with, treat this as a success condition. The application will need to detect this case and show a message that confirms that the email is verified, but that the user will need to sign in to complete.

Note: this is a breaking change, so we need to bump the minor (given this is a 0.x release)

[scotttrinh]

@jaclarke Sorry about missing this: the built-in UI needed this update, too, so: d6c1053 (#1145)

[scotttrinh]

Going to put this back in draft, it's not nearly ready:

• The core verify methods do not verify emails without a pkce verifier. They should be updated.
• We don't really have a way to signal that a sign-up -> verify --missing pkce--> sign in is really a sign up with more steps. I plan on adding the identity_id to the sign up response from the server so you can at least create your user before email verification. This will impact this interface.