Hotfix: init if mailbox is not set

[jsonsivar]

Description

This change double checks if the mailbox field is set on the SDK and init's it if it is not found. Even though the FE was initalizing it, for some reason the mailbox field was null so it was not sending the mails. This is a workaround so it re-inits it. @perfectmak let me know if you spot anything that could be the underlying issue.

Sidenote: also updated integration tests so we can test on dev via env vars as needed.

Fixes # (issue)
Mail not sending during share.

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?

• Unit Test
• Integration Test

Checklist:

• My code follows the style guidelines of this project
• I have made corresponding changes to the documentation
• 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

[perfectmak]

LGTM. Seems the tests are a failing due to the new TXL_HUB_URL environment variable