Fix bugs with Northstar auth verification.

[DFurnes]

What's this PR do?

This pull request includes cleanup and fixes to the Northstar auth verification & sync code:

🐛 The "verify" check was previously being run on newly registered users (before their profiles were synced to Northstar), resulting in "failed" validation and a bunch of users with NONE saved to their Northstar ID field. This PR moves this call to occur in a submit handler on the login form, rather than a Drupal hook. Also now just sends "username" and lets Northstar infer which type. (4a655c7)

📄 Updates docblocks to try to make it clearer when different hooks and submit handlers are run, since it was ambiguous from looking at the method names without plopping dpm hooks everywhere. (ab3ec96)

👉 Adds a helper method to save the "Northstar ID" profile field, since the syntax is kinda wonky and it's nice to not have the same code duplicated all over. (71c70e8)

🍃 Removes some commented out code from the Northstar Guzzle implementation, since it was making that file harder to skim. Once we revisit #5932, hopefully we can start using the Northstar PHP library here instead! (3f86eb6)

🍂 General tidying up. (c502379, a7df8ff, 939b0bb)

How should this be manually tested?

It's probably easiest to just test this on staging TBH. But there should be significantly fewer cases where users have NONE for their Northstar ID field, since it's now properly set on registration.

Any background context you want to provide?

👻

What are the relevant tickets?

References #6260.

---

For review: @angaither @weerd

[angaither]

we have some getters and setters in the user module, maybe this should live there?

[DFurnes]

Updated to use that method here in b27921d!

[angaither]

👍

[DFurnes]

Could've sworn I already posted this somewhere, but dropping it here for future reference.

Logging in to an existing account (from homepage or campaign signup) will verify user against POST auth/verify endpoint, and save returned ID to local field. This results in the following methods being called:

        dosomething_user_login_submit
        dosomething_user_northstar_login
        dosomething_northstar_verify_user
        dosomething_northstar_save_id_field

Registering a new user will send new user to the POST users/ endpoint, and save returned ID to local field. This is the result of the following methods being called:

        dosomething_user_new_user
        dosomething_northstar_register_user
        dosomething_northstar_save_id_field
        dosomething_northstar_update_user

Going to the “edit profile” page will send update to the POST users/drupal_id/:drupal_id endpoint:

        dosomething_northstar_update_user