Updates for the elixir version of SimEngine

[KaseyCantu]

JIRA covered:

• DX-1689 - Port shipengine-python to Elixir simengine implementation.

• DX-1701 - Related updates on Elixir SimEngine side

• Using the SimEngine endpoint: https://shipengine-web-api.herokuapp.com

• Update ID/URL/UTC to Id/Url/Utc

• Update ids to be base58

• Etc/get address/track package tests passing

• Note inconsistencies/unexpected values on the Elixir API service that would need to be updated

• (UPDATE: Ensure no trackingUrl assertions are commented out). Determine if when we would expect tracking_result.package.tracking_url to not be null (un-comment and resolve in test or elixir result). In tests/services/test_track_package.py the tests test_track_by_tracking_number_and_carrier_code and test_track_by_package_id the assert tracking_result.package.tracking_url is not None type assertions are commented out

• Update models to handle null values for string fields, and ensure no warnings come up on the tests for RuntimeWarning: NoneType object value of non-optional type phone detected etc. for the name/phone/company address fields

[nate-williams-auctane]

@KaseyCantu The tracking URL tests have been updates and are passing. The only thing left is making it so string variables are also handled as a null type, I figured you would be able to knock that out quicker than me, but let me know if I can help at all on that front!