Enhancement/add mailchimp api client

[MaxwellGarceau]

Description of the Change

This is part of #87. The work is separated to another branch as a proof of concept before spending more time on the idea.

• Add a FE Mailchimp client to Cypress tests to verify Mailchimp account interactions. Ensures successful form submission and full integration testing.
• Use .env.test for env variables
• Add health check for tests if Mailchimp client is unable to make requests
• Modularize Cypress commands

‼️ Environment changes needed ‼️

• Need to generate an API key for the test Mailchimp user in the CI/CD pipeline.
• Need to attach that API key to CYPRESS_MAILCHIMP_API_KEY as a Github secret
• Need to attach the server prefix to CYPRESS_MAILCHIMP_API_SERVER_PREFIX as a Github secret

How to test the Change

Run the cypress E2E tests

Changelog Entry

Added - Mailchimp client to testing to verify Mailchimp account interactions

Credits

Props @MaxwellGarceau

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[MaxwellGarceau]

In order to keep work moving I'm merging this branch into enhancement/update-critical-flows-with-e2e-test-coverage as a squash commit. Everyone's still out for the holidays.

Any comments can be addressed on the parent pull request #87.