Better security: Reduce the need for passing a service account key JSON file

[lucetre]

The use case you're trying to solve

Reduce the need for explicitly managing and passing a service account key JSON file. Better security practice.

Change to the action that would solve that use case

• Make firebaseServiceAccount input optional to activate Google ADC (application default credentials).
  feat: make firebaseServiceAccount input optional #398

Other considerations

N/A

[lucetre]

If we use the auth_token as serviceAccountToken, we are facing the below error simply speaking no way to use ADC;

  {
    "status": "error",
    "error": "Failed to authenticate, have you run \u001b[1mfirebase login\u001b[22m?"
  }{
    "status": "error",
    "error": "Failed to authenticate, have you run \u001b[1mfirebase login\u001b[22m?"
  }
  
  The process '/home/runner/_work/_tool/node/22.12.0/x64/bin/npx' failed with exit code 1
  Error: The process '/home/runner/_work/_tool/node/22.12.0/x64/bin/npx' failed with exit code 1
  {
    conclusion: 'failure',
    output: {
      title: 'Deploy preview failed',
      summary: "Error: The process '/home/runner/_work/_tool/node/22.12.0/x64/bin/npx' failed with exit code 1"
    }
  }

[pdewilde]

@lucetre Did that error come from you trying to run the version you had in your PR? #398

[lucetre]

No @pdewilde, the error actually occurred before.
PR #398 is my attempt to resolve that issue.