getJsonResponseBodyName is now an array

[mllemango]

WHY are these changes introduced?

Closes #258
Also FulfillmentRequest wouldn't have returned an object upon save, now it will

WHAT is this pull request doing?

We are making getJsonResponseBodyName an array to accept multiple possibilities that the API returns. This will let us resolve a few issues that we've faced before with our rest client

Type of change

• Patch: Bug (non-breaking change which fixes an issue)
• Minor: New feature (non-breaking change which adds functionality)
• Major: Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have added a changelog entry, prefixed by the type of change noted above
• I have added/updated tests for this change
• I have updated the documentation for public APIs from the library (if applicable)

[paulomarg]

Makes sense to me!