Use ACCOUNT_SIGNUP_FIELDS settings when available

[chellman]

AllAuth v65 has new signup field settings:

https://docs.allauth.org/en/latest/release-notes/recent.html#note-worthy-changes

Deprecation warnings are raised if you continue using the old settings, so it seems worth changing.

[vikito755]

When can this be merged? I'm seeing the same issue.

[gtlYashParmar]

@chellman
In current version i am stuck in one point. when i remove the username field from the signup fields. it is still asking for username while calling register api. i have tried with couple of different allauth configuration but not working. as i reviewed above this code is working well. i initially try with your code but it getting key error of username.

[Mte90]

@iMerica can you do a new release with this fix?

[samiashi]

@iMerica anything blocking to get this released?

[chellman]

@Yash-1511 and all watchers: massive apologies for how long this took. Changes made, review requested.