Fill DEV profile fields with MLH info on signup

[pmvenegas]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

This change prefills user profile data from MLH when an identity is linked, i.e. on OAuth registration. Specifically,

1. Since MLH does not provide a nickname, the suggested username is derived from the local-part of the user's email address. Previously, a random string was generated since the username was blank.
2. The scopes user:read:education, user:read:employment, and user:read:address are added to the MLH OAuth strategy, since these correspond to profile data we can use.
3. After an identity is created in Authentication::Authenticator#call, an worker is enqueued that:
   • fetches the user profile data with expansions from the MLH API
   • maps MLH fields to Forem profile fields (currently only location), with support for ProfileFields looked up by label: Work, Education, and Pronouns, if configured on the Forem instance.
   • fills in the corresponding fields if they are unassigned

Related Tickets & Documents

DEV-3339 (Jira)

QA Instructions, Screenshots, Recordings

This can be tested by creating a new Forem account with the MLH provider and confirming that profile fields set in MyMLH are used on Forem. MyMLH should prompt the user to enter data for the requested scopes if not already filled.

UI accessibility checklist

N/A

Added/updated tests?

We encourage you to keep the code coverage percentage at 80% and above.

• Yes
• No, and this is why: please replace this line with details on why tests
  have not been included
• I need help with writing tests

[optional] Are there any post deployment tasks we need to perform?

None

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[pmvenegas]

Removed to reflect actual MLH behavior.

[benhalpern]

Looks great