[SD-570] - Send basic auth header for webform submit

[jeffdowdle]

Issue: https://digital-vic.atlassian.net/browse/SD-570

What I did

• Only sends header when env vars are set to make sure it's backwards compatible

How to test

Checklist

For all PR's

• I've added relevant changes to the project Readme if needed
• I've updated the documentation site as needed
• I have added tests to cover my changes (if not applicable, please state why in a comment)

For new UI components only

• I have added a storybook story covering all variants
• I have checked a11y tab in storybook passes
• I have added cypress component tests (if the component is interactive)
• Any events are emitted on the event bus using emitRplEvent

[cypress]

ripple-framework    Run #2499

Run Properties:   Passed #2499  •  1b64b60257: feat(@dpc-sdp/ripple-tide-webform): send basic auth for webform submit if provid...

Project	ripple-framework
Branch Review	feature/SD-570-webform-submit-auth
Run status	Passed #2499
Run duration	10m 20s
Commit	1b64b60257: feat(@dpc-sdp/ripple-tide-webform): send basic auth for webform submit if provid...
Committer	Jeffrey Dowdle
View all properties for this run ↗︎

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Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	218
View all changes introduced in this branch ↗︎