Update for v5.7 and Fix Rebrandly API

[chrislarrycarl]

Description

Add housekeeping and an important fix

• Document support for WordPress v5.7 and update workflows
• Update dependencies
• Fix sanitize response from rebrandly API when looking up custom domains

Fixes # (issue)

Type of change

Please describe the type of change.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• TestUtmDotCodesActivation
• TestUtmDotCodesAjax
• TestUtmDotCodesIntegration
• TestUtmDotCodesShortenBitly
• TestUtmDotCodesShortenRebrandly
• TestUtmDotCodesUnit

Test Configuration:

• WordPress version: v5.7
• PHP version: v7.4
• MySQL version: 10.5.9-MariaDB

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I had fun writing this code

[codecov]

Codecov Report

Merging #51 (c203eb3) into main (b633414) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main      #51   +/-   ##
=========================================
  Coverage     79.95%   79.95%           
  Complexity      204      204           
=========================================
  Files             4        4           
  Lines           998      998           
=========================================
  Hits            798      798           
  Misses          200      200