users: refactor password reset flow.

The old password reset flow:

* User requests a password reset.
* Danbooru generates a password reset nonce.
* Danbooru emails user a password reset confirmation link.
* User follows link to password reset confirmation page.
* The link contains a nonce authenticating the user.
* User confirms password reset.
* Danbooru resets user's password to a random string.
* Danbooru emails user their new password in plaintext.

The new password reset flow:

* User requests a password reset.
* Danbooru emails user a password reset link.
* User follows link to password edit page.
* The link contains a signed_user_id param authenticating the user.
* User changes their own password.

app/logical/danbooru/message_verifier.rb

@@ -8,12 +8,12 @@ module Danbooru
       @verifier = ActiveSupport::MessageVerifier.new(secret, serializer: JSON, digest: "SHA256")
     end
 
-    def generate(*options)
-      verifier.generate(*options, purpose: purpose)
+    def generate(*args, **options)
+      verifier.generate(*args, purpose: purpose, **options)
     end
 
-    def verified(*options)
-      verifier.verified(*options, purpose: purpose)
+    def verify(*args, **options)
+      verifier.verify(*args, purpose: purpose, **options)
     end
   end
 end