Update reading test auth model

[kian99]

Description

The following change fixes an issue with test caching in JIMM. The current test code used to read the auth model would walk up the directory structure until finding a folder called "local", along the way it would read each directory. The issue with this is that the go test tool is smart enough to detect which files/directories are read by tests and invalidate the test cache when a potential input is changed. This meant that any change to a file, e.g. README.md would invalidate the test cache.

To resolve this, I've created .go file in the top level openfga folder/package where the authorisation_model.json file exists, embedded the file into the .go package and then referenced that package from the tests. This allows tests run from the root or any sub-directory to work.

Engineering checklist

Check only items that apply

• Documentation updated
• Covered by unit tests
• Covered by integration tests

[babakks]

Thanks for this.

[alesstimec]

LGTM with a comment