Javalab: pass host name to upload request and convert grid to JSON

[sanchitmalhotra126]

A couple of small fixes to the Javabuilder upload project code:

• pass the host name and set the Origin header on the PUT request - this is needed because the Javabuilder authorizer lambda uses the Origin header to decided which public key to use to decode the Auth token.
• convert the maze file to JSON. Currently, it's converted to a string in Ruby hash syntax which prevented Javabuilder from parsing it correctly.

Links

Testing story

Testing: confirmed that PUT requests succeeds on both localhost and via API Gateway (using a prototype API Gateway endpoint), and confirmed that the maze file is successfully parsed as JSON in Javabuilder.

Deployment strategy

Follow-up work

Privacy

Security

Caching

PR Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked