INT-889 Create Oauth page

[fuboki10]

PR Description

What this PR does

• User friendly index page

How to manually test

• APP_CONFIG=config/google.js yarn start

Reviewer Checklist (to be filled by reviewer)

Acceptance Criteria

• It is possible to understand the code without explanations.
• "Statement coverage" of the source code: >=70%. Deviation:
• All non-trivial methods are documented with docstrings.
• Names of classes, variables, methods, etc. follow naming conventions and are self-describing.
• Code does not contain hard-coded paths or labels.
• Errors are handled as close and specific as possible.
• Code reflects the architecture.
• Code reflects the specification.