api tests for preview flows

[yacineb]

[!IMPORTANT] Add API integration tests for preview flows using Deno, including setup, utilities, and configuration files.

• Tests:
  • Adds main_test.ts with tests for running and canceling flow previews using Deno.
  • Tests check job completion and cancellation status.
• Setup and Utilities:
  • Adds utils.ts for setting up test environment, generating API tokens, and checking job completion.
  • setup() function creates a test workspace and ensures API token is set.
• Configuration:
  • Adds deno.json for task definitions and module imports.
  • Adds deno.lock for dependency locking.
  • Adds README.md with instructions for running API tests using Deno.

^{This description was created by for 3cd2ca6bd5131b4934653a8548e64a563de84edc. It will automatically update as commits are pushed.}

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[rubenfiszel]

subsumed by 4626