Fix EYB user ingestion task

[oliverjwroberts]

Description of change

This PR fixes an issue where incoming EYB user data had null values for companyWebsite, which weren't being mapped to empty strings. This caused the RQ job to error due to violating the database field not null constraint for EYBLead.company_website.

Checklist

• Has this branch been rebased on top of the current main branch?

  Explanation

  The branch should not be stale or have conflicts at the time reviews are requested.

• Is the CircleCI build passing?

General points

Other things to check

• Make sure fixtures/test_data.yaml is maintained when updating models
• Consider the admin site when making changes to models
• Use select-/prefetch-related field lists in views and search apps, and update them when fields are added
• Make sure the README is updated e.g. when adding new environment variables

See docs/CONTRIBUTING.md for more guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.60%. Comparing base (0100779) to head (91c0876).
Report is 14 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5853   +/-   ##
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  Coverage   96.60%   96.60%           
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  Files        1047     1047           
  Lines       24920    24920           
  Branches     1649     1649           
=======================================
  Hits        24075    24075           
  Misses        689      689           
  Partials      156      156           

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